1080 lines
32 KiB
HTML
1080 lines
32 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
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"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
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<head>
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<meta http-equiv="Content-Type" content="application/xhtml+xml; charset=UTF-8" />
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<meta name="generator" content="AsciiDoc 10.2.0" />
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<title>gitpacking(7)</title>
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<style type="text/css">
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/* Shared CSS for AsciiDoc xhtml11 and html5 backends */
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/* Default font. */
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body {
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font-family: Georgia,serif;
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}
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/* Title font. */
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h1, h2, h3, h4, h5, h6,
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div.title, caption.title,
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thead, p.table.header,
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#toctitle,
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#author, #revnumber, #revdate, #revremark,
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#footer {
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font-family: Arial,Helvetica,sans-serif;
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}
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body {
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margin: 1em 5% 1em 5%;
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}
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a {
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color: blue;
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text-decoration: underline;
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}
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a:visited {
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color: fuchsia;
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}
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em {
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font-style: italic;
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color: navy;
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}
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strong {
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font-weight: bold;
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color: #083194;
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}
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h1, h2, h3, h4, h5, h6 {
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color: #527bbd;
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margin-top: 1.2em;
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margin-bottom: 0.5em;
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line-height: 1.3;
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}
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h1, h2, h3 {
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border-bottom: 2px solid silver;
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}
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h2 {
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padding-top: 0.5em;
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}
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h3 {
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float: left;
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}
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h3 + * {
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clear: left;
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}
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h5 {
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font-size: 1.0em;
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}
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div.sectionbody {
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margin-left: 0;
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}
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hr {
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border: 1px solid silver;
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}
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p {
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margin-top: 0.5em;
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margin-bottom: 0.5em;
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}
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ul, ol, li > p {
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margin-top: 0;
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}
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ul > li { color: #aaa; }
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ul > li > * { color: black; }
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.monospaced, code, pre {
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font-family: "Courier New", Courier, monospace;
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font-size: inherit;
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color: navy;
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padding: 0;
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margin: 0;
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}
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pre {
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white-space: pre-wrap;
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}
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#author {
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color: #527bbd;
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font-weight: bold;
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font-size: 1.1em;
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}
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#email {
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}
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#revnumber, #revdate, #revremark {
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}
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#footer {
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font-size: small;
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border-top: 2px solid silver;
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padding-top: 0.5em;
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margin-top: 4.0em;
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}
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#footer-text {
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float: left;
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padding-bottom: 0.5em;
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}
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#footer-badges {
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float: right;
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padding-bottom: 0.5em;
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}
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#preamble {
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margin-top: 1.5em;
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margin-bottom: 1.5em;
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}
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div.imageblock, div.exampleblock, div.verseblock,
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div.quoteblock, div.literalblock, div.listingblock, div.sidebarblock,
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div.admonitionblock {
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margin-top: 1.0em;
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margin-bottom: 1.5em;
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}
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div.admonitionblock {
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margin-top: 2.0em;
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margin-bottom: 2.0em;
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margin-right: 10%;
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color: #606060;
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}
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div.content { /* Block element content. */
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padding: 0;
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}
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/* Block element titles. */
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div.title, caption.title {
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color: #527bbd;
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font-weight: bold;
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text-align: left;
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margin-top: 1.0em;
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margin-bottom: 0.5em;
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}
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div.title + * {
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margin-top: 0;
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}
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td div.title:first-child {
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margin-top: 0.0em;
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}
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div.content div.title:first-child {
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margin-top: 0.0em;
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}
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div.content + div.title {
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margin-top: 0.0em;
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}
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div.sidebarblock > div.content {
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background: #ffffee;
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border: 1px solid #dddddd;
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border-left: 4px solid #f0f0f0;
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padding: 0.5em;
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}
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div.listingblock > div.content {
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border: 1px solid #dddddd;
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border-left: 5px solid #f0f0f0;
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background: #f8f8f8;
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padding: 0.5em;
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}
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div.quoteblock, div.verseblock {
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padding-left: 1.0em;
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margin-left: 1.0em;
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margin-right: 10%;
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border-left: 5px solid #f0f0f0;
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color: #888;
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}
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div.quoteblock > div.attribution {
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padding-top: 0.5em;
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text-align: right;
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}
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div.verseblock > pre.content {
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font-family: inherit;
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font-size: inherit;
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}
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div.verseblock > div.attribution {
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padding-top: 0.75em;
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text-align: left;
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}
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/* DEPRECATED: Pre version 8.2.7 verse style literal block. */
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div.verseblock + div.attribution {
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text-align: left;
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}
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div.admonitionblock .icon {
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vertical-align: top;
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font-size: 1.1em;
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font-weight: bold;
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text-decoration: underline;
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color: #527bbd;
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padding-right: 0.5em;
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}
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div.admonitionblock td.content {
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padding-left: 0.5em;
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border-left: 3px solid #dddddd;
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}
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div.exampleblock > div.content {
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border-left: 3px solid #dddddd;
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padding-left: 0.5em;
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}
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div.imageblock div.content { padding-left: 0; }
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span.image img { border-style: none; vertical-align: text-bottom; }
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a.image:visited { color: white; }
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dl {
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margin-top: 0.8em;
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margin-bottom: 0.8em;
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}
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dt {
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margin-top: 0.5em;
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margin-bottom: 0;
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font-style: normal;
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color: navy;
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}
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dd > *:first-child {
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margin-top: 0.1em;
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}
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ul, ol {
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list-style-position: outside;
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}
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ol.arabic {
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list-style-type: decimal;
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}
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ol.loweralpha {
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list-style-type: lower-alpha;
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}
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ol.upperalpha {
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list-style-type: upper-alpha;
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}
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ol.lowerroman {
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list-style-type: lower-roman;
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}
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ol.upperroman {
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list-style-type: upper-roman;
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}
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div.compact ul, div.compact ol,
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div.compact p, div.compact p,
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div.compact div, div.compact div {
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margin-top: 0.1em;
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margin-bottom: 0.1em;
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}
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tfoot {
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font-weight: bold;
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}
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td > div.verse {
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white-space: pre;
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}
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div.hdlist {
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margin-top: 0.8em;
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margin-bottom: 0.8em;
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}
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div.hdlist tr {
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padding-bottom: 15px;
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}
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dt.hdlist1.strong, td.hdlist1.strong {
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font-weight: bold;
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}
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td.hdlist1 {
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vertical-align: top;
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font-style: normal;
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padding-right: 0.8em;
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color: navy;
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}
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td.hdlist2 {
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vertical-align: top;
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}
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div.hdlist.compact tr {
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margin: 0;
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padding-bottom: 0;
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}
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.comment {
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background: yellow;
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}
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.footnote, .footnoteref {
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font-size: 0.8em;
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}
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span.footnote, span.footnoteref {
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vertical-align: super;
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}
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#footnotes {
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margin: 20px 0 20px 0;
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padding: 7px 0 0 0;
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}
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#footnotes div.footnote {
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margin: 0 0 5px 0;
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}
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#footnotes hr {
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border: none;
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border-top: 1px solid silver;
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height: 1px;
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text-align: left;
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margin-left: 0;
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width: 20%;
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min-width: 100px;
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}
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div.colist td {
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padding-right: 0.5em;
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padding-bottom: 0.3em;
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vertical-align: top;
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}
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div.colist td img {
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margin-top: 0.3em;
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}
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@media print {
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#footer-badges { display: none; }
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}
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#toc {
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margin-bottom: 2.5em;
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}
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#toctitle {
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color: #527bbd;
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font-size: 1.1em;
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font-weight: bold;
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margin-top: 1.0em;
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margin-bottom: 0.1em;
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}
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div.toclevel0, div.toclevel1, div.toclevel2, div.toclevel3, div.toclevel4 {
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margin-top: 0;
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margin-bottom: 0;
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}
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div.toclevel2 {
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margin-left: 2em;
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font-size: 0.9em;
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}
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div.toclevel3 {
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margin-left: 4em;
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font-size: 0.9em;
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}
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div.toclevel4 {
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margin-left: 6em;
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font-size: 0.9em;
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}
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span.aqua { color: aqua; }
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span.black { color: black; }
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span.blue { color: blue; }
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span.fuchsia { color: fuchsia; }
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span.gray { color: gray; }
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span.green { color: green; }
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span.lime { color: lime; }
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span.maroon { color: maroon; }
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span.navy { color: navy; }
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span.olive { color: olive; }
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span.purple { color: purple; }
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span.red { color: red; }
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span.silver { color: silver; }
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span.teal { color: teal; }
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span.white { color: white; }
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span.yellow { color: yellow; }
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span.aqua-background { background: aqua; }
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span.black-background { background: black; }
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span.blue-background { background: blue; }
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span.fuchsia-background { background: fuchsia; }
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span.gray-background { background: gray; }
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span.green-background { background: green; }
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span.lime-background { background: lime; }
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span.maroon-background { background: maroon; }
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span.navy-background { background: navy; }
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span.olive-background { background: olive; }
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span.purple-background { background: purple; }
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span.red-background { background: red; }
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span.silver-background { background: silver; }
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span.teal-background { background: teal; }
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span.white-background { background: white; }
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span.yellow-background { background: yellow; }
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span.big { font-size: 2em; }
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span.small { font-size: 0.6em; }
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span.underline { text-decoration: underline; }
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span.overline { text-decoration: overline; }
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span.line-through { text-decoration: line-through; }
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div.unbreakable { page-break-inside: avoid; }
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/*
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* xhtml11 specific
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*
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* */
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div.tableblock {
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margin-top: 1.0em;
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margin-bottom: 1.5em;
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}
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div.tableblock > table {
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border: 3px solid #527bbd;
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}
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thead, p.table.header {
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font-weight: bold;
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color: #527bbd;
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}
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p.table {
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margin-top: 0;
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}
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/* Because the table frame attribute is overridden by CSS in most browsers. */
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div.tableblock > table[frame="void"] {
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border-style: none;
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}
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div.tableblock > table[frame="hsides"] {
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border-left-style: none;
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border-right-style: none;
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}
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div.tableblock > table[frame="vsides"] {
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border-top-style: none;
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border-bottom-style: none;
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}
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/*
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* html5 specific
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*
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* */
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table.tableblock {
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margin-top: 1.0em;
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margin-bottom: 1.5em;
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}
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thead, p.tableblock.header {
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font-weight: bold;
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color: #527bbd;
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}
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p.tableblock {
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margin-top: 0;
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}
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table.tableblock {
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border-width: 3px;
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border-spacing: 0px;
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border-style: solid;
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border-color: #527bbd;
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border-collapse: collapse;
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}
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th.tableblock, td.tableblock {
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border-width: 1px;
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padding: 4px;
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border-style: solid;
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border-color: #527bbd;
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}
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table.tableblock.frame-topbot {
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border-left-style: hidden;
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border-right-style: hidden;
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}
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table.tableblock.frame-sides {
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border-top-style: hidden;
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border-bottom-style: hidden;
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}
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table.tableblock.frame-none {
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border-style: hidden;
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}
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th.tableblock.halign-left, td.tableblock.halign-left {
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text-align: left;
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}
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th.tableblock.halign-center, td.tableblock.halign-center {
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text-align: center;
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}
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th.tableblock.halign-right, td.tableblock.halign-right {
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text-align: right;
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}
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th.tableblock.valign-top, td.tableblock.valign-top {
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vertical-align: top;
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}
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th.tableblock.valign-middle, td.tableblock.valign-middle {
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vertical-align: middle;
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}
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th.tableblock.valign-bottom, td.tableblock.valign-bottom {
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vertical-align: bottom;
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}
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/*
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* manpage specific
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*
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* */
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body.manpage h1 {
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padding-top: 0.5em;
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padding-bottom: 0.5em;
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border-top: 2px solid silver;
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border-bottom: 2px solid silver;
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}
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body.manpage h2 {
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border-style: none;
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}
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body.manpage div.sectionbody {
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margin-left: 3em;
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}
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@media print {
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body.manpage div#toc { display: none; }
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}
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</style>
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<script type="text/javascript">
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/*<+'])');
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// Function that scans the DOM tree for header elements (the DOM2
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// nodeIterator API would be a better technique but not supported by all
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// browsers).
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var iterate = function (el) {
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for (var i = el.firstChild; i != null; i = i.nextSibling) {
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if (i.nodeType == 1 /* Node.ELEMENT_NODE */) {
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var mo = re.exec(i.tagName);
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if (mo && (i.getAttribute("class") || i.getAttribute("className")) != "float") {
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result[result.length] = new TocEntry(i, getText(i), mo[1]-1);
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}
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iterate(i);
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}
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}
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}
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iterate(el);
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return result;
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}
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var toc = document.getElementById("toc");
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if (!toc) {
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return;
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}
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// Delete existing TOC entries in case we're reloading the TOC.
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var tocEntriesToRemove = [];
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var i;
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for (i = 0; i < toc.childNodes.length; i++) {
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var entry = toc.childNodes[i];
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if (entry.nodeName.toLowerCase() == 'div'
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&& entry.getAttribute("class")
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&& entry.getAttribute("class").match(/^toclevel/))
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tocEntriesToRemove.push(entry);
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}
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for (i = 0; i < tocEntriesToRemove.length; i++) {
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toc.removeChild(tocEntriesToRemove[i]);
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}
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// Rebuild TOC entries.
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var entries = tocEntries(document.getElementById("content"), toclevels);
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for (var i = 0; i < entries.length; ++i) {
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var entry = entries[i];
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if (entry.element.id == "")
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entry.element.id = "_toc_" + i;
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var a = document.createElement("a");
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/*]]>*/
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|
|
</head>
|
|
<body class="manpage">
|
|
<div id="header">
|
|
<h1>
|
|
gitpacking(7) Manual Page
|
|
</h1>
|
|
<h2>NAME</h2>
|
|
<div class="sectionbody">
|
|
<p>gitpacking -
|
|
Advanced concepts related to packing in Git
|
|
</p>
|
|
</div>
|
|
</div>
|
|
<div id="content">
|
|
<div class="sect1">
|
|
<h2 id="_synopsis">SYNOPSIS</h2>
|
|
<div class="sectionbody">
|
|
<div class="paragraph"><p>gitpacking</p></div>
|
|
</div>
|
|
</div>
|
|
<div class="sect1">
|
|
<h2 id="_description">DESCRIPTION</h2>
|
|
<div class="sectionbody">
|
|
<div class="paragraph"><p>This document aims to describe some advanced concepts related to packing
|
|
in Git.</p></div>
|
|
<div class="paragraph"><p>Many concepts are currently described scattered between manual pages of
|
|
various Git commands, including <a href="git-pack-objects.html">git-pack-objects(1)</a>,
|
|
<a href="git-repack.html">git-repack(1)</a>, and others, as well as <a href="gitformat-pack.html">gitformat-pack(5)</a>,
|
|
and parts of the <code>Documentation/technical</code> tree.</p></div>
|
|
<div class="paragraph"><p>There are many aspects of packing in Git that are not covered in this
|
|
document that instead live in the aforementioned areas. Over time, those
|
|
scattered bits may coalesce into this document.</p></div>
|
|
</div>
|
|
</div>
|
|
<div class="sect1">
|
|
<h2 id="_pseudo_merge_bitmaps">Pseudo-merge bitmaps</h2>
|
|
<div class="sectionbody">
|
|
<div class="admonitionblock">
|
|
<table><tr>
|
|
<td class="icon">
|
|
<div class="title">Note</div>
|
|
</td>
|
|
<td class="content">Pseudo-merge bitmaps are considered an experimental feature, so
|
|
the configuration and many of the ideas are subject to change.</td>
|
|
</tr></table>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_background">Background</h3>
|
|
<div class="paragraph"><p>Reachability bitmaps are most efficient when we have on-disk stored
|
|
bitmaps for one or more of the starting points of a traversal. For this
|
|
reason, Git prefers storing bitmaps for commits at the tips of refs,
|
|
because traversals tend to start with those points.</p></div>
|
|
<div class="paragraph"><p>But if you have a large number of refs, it’s not feasible to store a
|
|
bitmap for <em>every</em> ref tip. It takes up space, and just OR-ing all of
|
|
those bitmaps together is expensive.</p></div>
|
|
<div class="paragraph"><p>One way we can deal with that is to create bitmaps that represent
|
|
<em>groups</em> of refs. When a traversal asks about the entire group, then we
|
|
can use this single bitmap instead of considering each ref individually.
|
|
Because these bitmaps represent the set of objects which would be
|
|
reachable in a hypothetical merge of all of the commits, we call them
|
|
pseudo-merge bitmaps.</p></div>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_overview">Overview</h3>
|
|
<div class="paragraph"><p>A "pseudo-merge bitmap" is used to refer to a pair of bitmaps, as
|
|
follows:</p></div>
|
|
<div class="dlist"><dl>
|
|
<dt class="hdlist1">
|
|
Commit bitmap
|
|
</dt>
|
|
<dd>
|
|
<p>
|
|
A bitmap whose set bits describe the set of commits included in the
|
|
pseudo-merge’s "merge" bitmap (as below).
|
|
</p>
|
|
</dd>
|
|
<dt class="hdlist1">
|
|
Merge bitmap
|
|
</dt>
|
|
<dd>
|
|
<p>
|
|
A bitmap whose set bits describe the reachability closure over the set
|
|
of commits in the pseudo-merge’s "commits" bitmap (as above). An
|
|
identical bitmap would be generated for an octopus merge with the same
|
|
set of parents as described in the commits bitmap.
|
|
</p>
|
|
</dd>
|
|
</dl></div>
|
|
<div class="paragraph"><p>Pseudo-merge bitmaps can accelerate bitmap traversals when all commits
|
|
for a given pseudo-merge are listed on either side of the traversal,
|
|
either directly (by explicitly asking for them as part of the <code>HAVES</code>
|
|
or <code>WANTS</code>) or indirectly (by encountering them during a fill-in
|
|
traversal).</p></div>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_use_cases">Use-cases</h3>
|
|
<div class="paragraph"><p>For example, suppose there exists a pseudo-merge bitmap with a large
|
|
number of commits, all of which are listed in the <code>WANTS</code> section of
|
|
some bitmap traversal query. When pseudo-merge bitmaps are enabled, the
|
|
bitmap machinery can quickly determine there is a pseudo-merge which
|
|
satisfies some subset of the wanted objects on either side of the query.
|
|
Then, we can inflate the EWAH-compressed bitmap, and <code>OR</code> it in to the
|
|
resulting bitmap. By contrast, without pseudo-merge bitmaps, we would
|
|
have to repeat the decompression and <code>OR</code>-ing step over a potentially
|
|
large number of individual bitmaps, which can take proportionally more
|
|
time.</p></div>
|
|
<div class="paragraph"><p>Another benefit of pseudo-merges arises when there is some combination
|
|
of (a) a large number of references, with (b) poor bitmap coverage, and
|
|
(c) deep, nested trees, making fill-in traversal relatively expensive.
|
|
For example, suppose that there are a large enough number of tags where
|
|
bitmapping each of the tags individually is infeasible. Without
|
|
pseudo-merge bitmaps, computing the result of, say, <code>git</code> <code>rev-list</code>
|
|
<code>--use-bitmap-index</code> <code>--count</code> <code>--objects</code> <code>--tags</code> would likely require a
|
|
large amount of fill-in traversal. But when a large quantity of those
|
|
tags are stored together in a pseudo-merge bitmap, the bitmap machinery
|
|
can take advantage of the fact that we only care about the union of
|
|
objects reachable from all of those tags, and answer the query much
|
|
faster.</p></div>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_configuration">Configuration</h3>
|
|
<div class="paragraph"><p>Reference tips are grouped into different pseudo-merge groups according
|
|
to two criteria. A reference name matches one or more of the defined
|
|
pseudo-merge patterns, and optionally one or more capture groups within
|
|
that pattern which further partition the group.</p></div>
|
|
<div class="paragraph"><p>Within a group, commits may be considered "stable", or "unstable"
|
|
depending on their age. These are adjusted by setting the
|
|
<code>bitmapPseudoMerge.</code><em><name></em><code>.stableThreshold</code> and
|
|
<code>bitmapPseudoMerge.</code><em><name></em><code>.threshold</code> configuration values, respectively.</p></div>
|
|
<div class="paragraph"><p>All stable commits are grouped into pseudo-merges of equal size
|
|
(<code>bitmapPseudoMerge.</code><em><name></em><code>.stableSize</code>). If the <code>stableSize</code>
|
|
configuration is set to, say, 100, then the first 100 commits (ordered
|
|
by committer date) which are older than the <code>stableThreshold</code> value will
|
|
form one group, the next 100 commits will form another group, and so on.</p></div>
|
|
<div class="paragraph"><p>Among unstable commits, the pseudo-merge machinery will attempt to
|
|
combine older commits into large groups as opposed to newer commits
|
|
which will appear in smaller groups. This is based on the heuristic that
|
|
references whose tip commit is older are less likely to be modified to
|
|
point at a different commit than a reference whose tip commit is newer.</p></div>
|
|
<div class="paragraph"><p>The size of groups is determined by a power-law decay function, and the
|
|
decay parameter roughly corresponds to "k" in <code>f</code>(<code>n</code>) <code>=</code> <code>C*n^</code>(<code>-k/100</code>),
|
|
where <code>f</code>(<code>n</code>) describes the size of the <code>n</code>-th pseudo-merge group. The
|
|
sample rate controls what percentage of eligible commits are considered
|
|
as candidates. The threshold parameter indicates the minimum age (so as
|
|
to avoid including too-recent commits in a pseudo-merge group, making it
|
|
less likely to be valid). The "maxMerges" parameter sets an upper-bound
|
|
on the number of pseudo-merge commits an individual group</p></div>
|
|
<div class="paragraph"><p>The "stable"-related parameters control "stable" pseudo-merge groups,
|
|
comprised of a fixed number of commits which are older than the
|
|
configured "stable threshold" value and may be grouped together in
|
|
chunks of "stableSize" in order of age.</p></div>
|
|
<div class="paragraph"><p>The exact configuration for pseudo-merges is as follows:</p></div>
|
|
<div class="admonitionblock">
|
|
<table><tr>
|
|
<td class="icon">
|
|
<div class="title">Note</div>
|
|
</td>
|
|
<td class="content">The configuration options in <code>bitmapPseudoMerge.*</code> are considered
|
|
EXPERIMENTAL and may be subject to change or be removed entirely in the
|
|
future. For more information about the pseudo-merge bitmap feature, see
|
|
the "Pseudo-merge bitmaps" section of <a href="gitpacking.html">gitpacking(7)</a>.</td>
|
|
</tr></table>
|
|
</div>
|
|
<div class="dlist"><dl>
|
|
<dt class="hdlist1">
|
|
bitmapPseudoMerge.<name>.pattern
|
|
</dt>
|
|
<dd>
|
|
<p>
|
|
Regular expression used to match reference names. Commits
|
|
pointed to by references matching this pattern (and meeting
|
|
the below criteria, like <code>bitmapPseudoMerge.</code><em><name></em><code>.sampleRate</code>
|
|
and <code>bitmapPseudoMerge.</code><em><name></em><code>.threshold</code>) will be considered
|
|
for inclusion in a pseudo-merge bitmap.
|
|
</p>
|
|
<div class="paragraph"><p>Commits are grouped into pseudo-merge groups based on whether or not
|
|
any reference(s) that point at a given commit match the pattern, which
|
|
is an extended regular expression.</p></div>
|
|
<div class="paragraph"><p>Within a pseudo-merge group, commits may be further grouped into
|
|
sub-groups based on the capture groups in the pattern. These
|
|
sub-groupings are formed from the regular expressions by concatenating
|
|
any capture groups from the regular expression, with a <em>-</em> dash in
|
|
between.</p></div>
|
|
<div class="paragraph"><p>For example, if the pattern is <code>refs/tags/</code>, then all tags (provided
|
|
they meet the below criteria) will be considered candidates for the
|
|
same pseudo-merge group. However, if the pattern is instead
|
|
<code>refs/remotes/</code>([<code>0-9</code>])<code>+/tags/</code>, then tags from different remotes will
|
|
be grouped into separate pseudo-merge groups, based on the remote
|
|
number.</p></div>
|
|
</dd>
|
|
<dt class="hdlist1">
|
|
bitmapPseudoMerge.<name>.decay
|
|
</dt>
|
|
<dd>
|
|
<p>
|
|
Determines the rate at which consecutive pseudo-merge bitmap
|
|
groups decrease in size. Must be non-negative. This parameter
|
|
can be thought of as <code>k</code> in the function <code>f</code>(<code>n</code>) <code>=</code> <code>C</code> <code>*</code> <code>n^-k</code>,
|
|
where <code>f</code>(<code>n</code>) is the size of the `n`th group.
|
|
</p>
|
|
<div class="paragraph"><p>Setting the decay rate equal to <code>0</code> will cause all groups to be the
|
|
same size. Setting the decay rate equal to <code>1</code> will cause the <code>n</code>`th
|
|
<code>group</code> <code>to</code> <code>be</code> `1/n the size of the initial group. Higher values of the
|
|
decay rate cause consecutive groups to shrink at an increasing rate.
|
|
The default is <code>1</code>.</p></div>
|
|
<div class="paragraph"><p>If all groups are the same size, it is possible that groups containing
|
|
newer commits will be able to be used less often than earlier groups,
|
|
since it is more likely that the references pointing at newer commits
|
|
will be updated more often than a reference pointing at an old commit.</p></div>
|
|
</dd>
|
|
<dt class="hdlist1">
|
|
bitmapPseudoMerge.<name>.sampleRate
|
|
</dt>
|
|
<dd>
|
|
<p>
|
|
Determines the proportion of non-bitmapped commits (among
|
|
reference tips) which are selected for inclusion in an
|
|
unstable pseudo-merge bitmap. Must be between <code>0</code> and <code>1</code>
|
|
(inclusive). The default is <code>1</code>.
|
|
</p>
|
|
</dd>
|
|
<dt class="hdlist1">
|
|
bitmapPseudoMerge.<name>.threshold
|
|
</dt>
|
|
<dd>
|
|
<p>
|
|
Determines the minimum age of non-bitmapped commits (among
|
|
reference tips, as above) which are candidates for inclusion
|
|
in an unstable pseudo-merge bitmap. The default is
|
|
<code>1.week.ago</code>.
|
|
</p>
|
|
</dd>
|
|
<dt class="hdlist1">
|
|
bitmapPseudoMerge.<name>.maxMerges
|
|
</dt>
|
|
<dd>
|
|
<p>
|
|
Determines the maximum number of pseudo-merge commits among
|
|
which commits may be distributed.
|
|
</p>
|
|
<div class="paragraph"><p>For pseudo-merge groups whose pattern does not contain any capture
|
|
groups, this setting is applied for all commits matching the regular
|
|
expression. For patterns that have one or more capture groups, this
|
|
setting is applied for each distinct capture group.</p></div>
|
|
<div class="paragraph"><p>For example, if your capture group is <code>refs/tags/</code>, then this setting
|
|
will distribute all tags into a maximum of <code>maxMerges</code> pseudo-merge
|
|
commits. However, if your capture group is, say,
|
|
<code>refs/remotes/</code>([<code>0-9</code>]<code>+</code>)<code>/tags/</code>, then this setting will be applied to
|
|
each remote’s set of tags individually.</p></div>
|
|
<div class="paragraph"><p>Must be non-negative. The default value is 64.</p></div>
|
|
</dd>
|
|
<dt class="hdlist1">
|
|
bitmapPseudoMerge.<name>.stableThreshold
|
|
</dt>
|
|
<dd>
|
|
<p>
|
|
Determines the minimum age of commits (among reference tips,
|
|
as above, however stable commits are still considered
|
|
candidates even when they have been covered by a bitmap) which
|
|
are candidates for a stable a pseudo-merge bitmap. The default
|
|
is <code>1.month.ago</code>.
|
|
</p>
|
|
<div class="paragraph"><p>Setting this threshold to a smaller value (e.g., 1.week.ago) will cause
|
|
more stable groups to be generated (which impose a one-time generation
|
|
cost) but those groups will likely become stale over time. Using a
|
|
larger value incurs the opposite penalty (fewer stable groups which are
|
|
more useful).</p></div>
|
|
</dd>
|
|
<dt class="hdlist1">
|
|
bitmapPseudoMerge.<name>.stableSize
|
|
</dt>
|
|
<dd>
|
|
<p>
|
|
Determines the size (in number of commits) of a stable
|
|
psuedo-merge bitmap. The default is <code>512</code>.
|
|
</p>
|
|
</dd>
|
|
</dl></div>
|
|
</div>
|
|
<div class="sect2">
|
|
<h3 id="_examples">Examples</h3>
|
|
<div class="paragraph"><p>Suppose that you have a repository with a large number of references,
|
|
and you want a bare-bones configuration of pseudo-merge bitmaps that
|
|
will enhance bitmap coverage of the <code>refs/</code> namespace. You may start
|
|
with a configuration like so:</p></div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre><code>[bitmapPseudoMerge "all"]
|
|
pattern = "refs/"
|
|
threshold = now
|
|
stableThreshold = never
|
|
sampleRate = 100
|
|
maxMerges = 64</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>This will create pseudo-merge bitmaps for all references, regardless of
|
|
their age, and group them into 64 pseudo-merge commits.</p></div>
|
|
<div class="paragraph"><p>If you wanted to separate tags from branches when generating
|
|
pseudo-merge commits, you would instead define the pattern with a
|
|
capture group, like so:</p></div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre><code>[bitmapPseudoMerge "all"]
|
|
pattern = "refs/(heads/tags)/"</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>Suppose instead that you are working in a fork-network repository, with
|
|
each fork specified by some numeric ID, and whose refs reside in
|
|
<code>refs/virtual/NNN/</code> (where <code>NNN</code> is the numeric ID corresponding to some
|
|
fork) in the network. In this instance, you may instead write something
|
|
like:</p></div>
|
|
<div class="listingblock">
|
|
<div class="content">
|
|
<pre><code>[bitmapPseudoMerge "all"]
|
|
pattern = "refs/virtual/([0-9]+)/(heads|tags)/"
|
|
threshold = now
|
|
stableThreshold = never
|
|
sampleRate = 100
|
|
maxMerges = 64</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>Which would generate pseudo-merge group identifiers like "1234-heads",
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and "5678-tags" (for branches in fork "1234", and tags in remote "5678",
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respectively).</p></div>
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</div>
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</div>
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</div>
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<div class="sect1">
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<h2 id="_see_also">SEE ALSO</h2>
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<div class="sectionbody">
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<div class="paragraph"><p><a href="git-pack-objects.html">git-pack-objects(1)</a>
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<a href="git-repack.html">git-repack(1)</a></p></div>
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</div>
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</div>
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<div class="sect1">
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<h2 id="_git">GIT</h2>
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<div class="sectionbody">
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<div class="paragraph"><p>Part of the <a href="git.html">git(1)</a> suite</p></div>
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</div>
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</div>
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</div>
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<div id="footnotes"><hr /></div>
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<div id="footer">
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<div id="footer-text">
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Last updated
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2025-08-18 02:18:23 CEST
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