1033 lines
30 KiB
HTML
1033 lines
30 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>How to revert a faulty merge</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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|
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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 {
|
|
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;
|
|
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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|
}
|
|
|
|
@media print {
|
|
body.manpage div#toc { display: none; }
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|
}
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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
|
|
// nodeIterator API would be a better technique but not supported by all
|
|
// browsers).
|
|
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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}
|
|
|
|
var toc = document.getElementById("toc");
|
|
if (!toc) {
|
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return;
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}
|
|
|
|
// Delete existing TOC entries in case we're reloading the TOC.
|
|
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];
|
|
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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}
|
|
for (i = 0; i < tocEntriesToRemove.length; i++) {
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toc.removeChild(tocEntriesToRemove[i]);
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}
|
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|
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// Rebuild TOC entries.
|
|
var entries = tocEntries(document.getElementById("content"), toclevels);
|
|
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;
|
|
var a = document.createElement("a");
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</head>
|
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<body class="article">
|
|
<div id="header">
|
|
<h1>How to revert a faulty merge</h1>
|
|
<span id="revdate"></span>
|
|
</div>
|
|
<div id="content">
|
|
<div id="preamble">
|
|
<div class="sectionbody">
|
|
<div class="paragraph"><p>Alan <<a href="mailto:alan@clueserver.org">alan@clueserver.org</a>> said:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>I have a master branch. We have a branch off of that that some
|
|
developers are doing work on. They claim it is ready. We merge it
|
|
into the master branch. It breaks something so we revert the merge.
|
|
They make changes to the code. they get it to a point where they say
|
|
it is ok and we merge again.</code></pre>
|
|
</div></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>When examined, we find that code changes made before the revert are
|
|
not in the master branch, but code changes after are in the master
|
|
branch.</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>and asked for help recovering from this situation.</p></div>
|
|
<div class="paragraph"><p>The history immediately after the "revert of the merge" would look like
|
|
this:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>---o---o---o---M---x---x---W
|
|
/
|
|
---A---B</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>where A and B are on the side development that was not so good, M is the
|
|
merge that brings these premature changes into the mainline, x are changes
|
|
unrelated to what the side branch did and already made on the mainline,
|
|
and W is the "revert of the merge M" (doesn’t W look M upside down?).
|
|
IOW, "diff <code>W^</code><code>..</code><code>W</code>" is similar to "diff <code>-R</code> <code>M^</code><code>..</code><code>M</code>".</p></div>
|
|
<div class="paragraph"><p>Such a "revert" of a merge can be made with:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>$ git revert -m 1 M</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>After the developers of the side branch fix their mistakes, the history
|
|
may look like this:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>---o---o---o---M---x---x---W---x
|
|
/
|
|
---A---B-------------------C---D</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>where C and D are to fix what was broken in A and B, and you may already
|
|
have some other changes on the mainline after W.</p></div>
|
|
<div class="paragraph"><p>If you merge the updated side branch (with D at its tip), none of the
|
|
changes made in A or B will be in the result, because they were reverted
|
|
by W. That is what Alan saw.</p></div>
|
|
<div class="paragraph"><p>Linus explains the situation:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>Reverting a regular commit just effectively undoes what that commit
|
|
did, and is fairly straightforward. But reverting a merge commit also
|
|
undoes the _data_ that the commit changed, but it does absolutely
|
|
nothing to the effects on _history_ that the merge had.</code></pre>
|
|
</div></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>So the merge will still exist, and it will still be seen as joining
|
|
the two branches together, and future merges will see that merge as
|
|
the last shared state - and the revert that reverted the merge brought
|
|
in will not affect that at all.</code></pre>
|
|
</div></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>So a "revert" undoes the data changes, but it's very much _not_ an
|
|
"undo" in the sense that it doesn't undo the effects of a commit on
|
|
the repository history.</code></pre>
|
|
</div></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>So if you think of "revert" as "undo", then you're going to always
|
|
miss this part of reverts. Yes, it undoes the data, but no, it doesn't
|
|
undo history.</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>In such a situation, you would want to first revert the previous revert,
|
|
which would make the history look like this:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>---o---o---o---M---x---x---W---x---Y
|
|
/
|
|
---A---B-------------------C---D</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>where Y is the revert of W. Such a "revert of the revert" can be done
|
|
with:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>$ git revert W</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>This history would (ignoring possible conflicts between what W and W..Y
|
|
changed) be equivalent to not having W or Y at all in the history:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>---o---o---o---M---x---x-------x----
|
|
/
|
|
---A---B-------------------C---D</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>and merging the side branch again will not have conflict arising from an
|
|
earlier revert and revert of the revert.</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>---o---o---o---M---x---x-------x-------*
|
|
/ /
|
|
---A---B-------------------C---D</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>Of course the changes made in C and D still can conflict with what was
|
|
done by any of the x, but that is just a normal merge conflict.</p></div>
|
|
<div class="paragraph"><p>On the other hand, if the developers of the side branch discarded their
|
|
faulty A and B, and redone the changes on top of the updated mainline
|
|
after the revert, the history would have looked like this:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>---o---o---o---M---x---x---W---x---x
|
|
/ \
|
|
---A---B A'--B'--C'</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>If you reverted the revert in such a case as in the previous example:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>---o---o---o---M---x---x---W---x---x---Y---*
|
|
/ \ /
|
|
---A---B A'--B'--C'</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>where Y is the revert of W, A' and B' are rerolled A and B, and there may
|
|
also be a further fix-up C' on the side branch. "diff <code>Y^</code><code>..</code><code>Y</code>" is similar
|
|
to "diff <code>-R</code> <code>W^</code><code>..</code><code>W</code>" (which in turn means it is similar to "diff <code>M^</code><code>..</code><code>M</code>"),
|
|
and "diff <code>A</code>'^<code>..</code><code>C</code>'" by definition would be similar but different from that,
|
|
because it is a rerolled series of the earlier change. There will be a
|
|
lot of overlapping changes that result in conflicts. So do not do "revert
|
|
of revert" blindly without thinking..</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>---o---o---o---M---x---x---W---x---x
|
|
/ \
|
|
---A---B A'--B'--C'</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>In the history with rebased side branch, W (and M) are behind the merge
|
|
base of the updated branch and the tip of the mainline, and they should
|
|
merge without the past faulty merge and its revert getting in the way.</p></div>
|
|
<div class="paragraph"><p>To recap, these are two very different scenarios, and they want two very
|
|
different resolution strategies:</p></div>
|
|
<div class="ulist"><ul>
|
|
<li>
|
|
<p>
|
|
If the faulty side branch was fixed by adding corrections on top, then
|
|
doing a revert of the previous revert would be the right thing to do.
|
|
</p>
|
|
</li>
|
|
<li>
|
|
<p>
|
|
If the faulty side branch whose effects were discarded by an earlier
|
|
revert of a merge was rebuilt from scratch (i.e. rebasing and fixing,
|
|
as you seem to have interpreted), then re-merging the result without
|
|
doing anything else fancy would be the right thing to do.
|
|
(See the ADDENDUM below for how to rebuild a branch from scratch
|
|
without changing its original branching-off point.)
|
|
</p>
|
|
</li>
|
|
</ul></div>
|
|
<div class="paragraph"><p>However, there are things to keep in mind when reverting a merge (and
|
|
reverting such a revert).</p></div>
|
|
<div class="paragraph"><p>For example, think about what reverting a merge (and then reverting the
|
|
revert) does to bisectability. Ignore the fact that the revert of a revert
|
|
is undoing it - just think of it as a "single commit that does a lot".
|
|
Because that is what it does.</p></div>
|
|
<div class="paragraph"><p>When you have a problem you are chasing down, and you hit a "revert this
|
|
merge", what you’re hitting is essentially a single commit that contains
|
|
all the changes (but obviously in reverse) of all the commits that got
|
|
merged. So it’s debugging hell, because now you don’t have lots of small
|
|
changes that you can try to pinpoint which <em>part</em> of it changes.</p></div>
|
|
<div class="paragraph"><p>But does it all work? Sure it does. You can revert a merge, and from a
|
|
purely technical angle, Git did it very naturally and had no real
|
|
troubles. It just considered it a change from "state before merge" to
|
|
"state after merge", and that was it. Nothing complicated, nothing odd,
|
|
nothing really dangerous. Git will do it without even thinking about it.</p></div>
|
|
<div class="paragraph"><p>So from a technical angle, there’s nothing wrong with reverting a merge,
|
|
but from a workflow angle it’s something that you generally should try to
|
|
avoid.</p></div>
|
|
<div class="paragraph"><p>If at all possible, for example, if you find a problem that got merged
|
|
into the main tree, rather than revert the merge, try <em>really</em> hard to
|
|
bisect the problem down into the branch you merged, and just fix it, or
|
|
try to revert the individual commit that caused it.</p></div>
|
|
<div class="paragraph"><p>Yes, it’s more complex, and no, it’s not always going to work (sometimes
|
|
the answer is: "oops, I really shouldn’t have merged it, because it wasn’t
|
|
ready yet, and I really need to undo <em>all</em> of the merge"). So then you
|
|
really should revert the merge, but when you want to re-do the merge, you
|
|
now need to do it by reverting the revert.</p></div>
|
|
<div class="paragraph"><p>ADDENDUM</p></div>
|
|
<div class="paragraph"><p>Sometimes you have to rewrite one of a topic branch’s commits <strong>and</strong> you can’t
|
|
change the topic’s branching-off point. Consider the following situation:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>P---o---o---M---x---x---W---x
|
|
\ /
|
|
A---B---C</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>where commit W reverted commit M because it turned out that commit B was wrong
|
|
and needs to be rewritten, but you need the rewritten topic to still branch
|
|
from commit P (perhaps P is a branching-off point for yet another branch, and
|
|
you want be able to merge the topic into both branches).</p></div>
|
|
<div class="paragraph"><p>The natural thing to do in this case is to checkout the A-B-C branch and use
|
|
"rebase -i P" to change commit B. However this does not rewrite commit A,
|
|
because "rebase -i" by default fast-forwards over any initial commits selected
|
|
with the "pick" command. So you end up with this:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>P---o---o---M---x---x---W---x
|
|
\ /
|
|
A---B---C <-- old branch
|
|
\
|
|
B'---C' <-- naively rewritten branch</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>To merge A-B'-C' into the mainline branch you would still have to first revert
|
|
commit W in order to pick up the changes in A, but then it’s likely that the
|
|
changes in B' will conflict with the original B changes re-introduced by the
|
|
reversion of W.</p></div>
|
|
<div class="paragraph"><p>However, you can avoid these problems if you recreate the entire branch,
|
|
including commit A:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code> A'---B'---C' <-- completely rewritten branch
|
|
/
|
|
P---o---o---M---x---x---W---x
|
|
\ /
|
|
A---B---C</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>You can merge A'-B'-C' into the mainline branch without worrying about first
|
|
reverting W. Mainline’s history would look like this:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code> A'---B'---C'------------------
|
|
/ \
|
|
P---o---o---M---x---x---W---x---M2
|
|
\ /
|
|
A---B---C</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>But if you don’t actually need to change commit A, then you need some way to
|
|
recreate it as a new commit with the same changes in it. The rebase command’s
|
|
--no-ff option provides a way to do this:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>$ git rebase [-i] --no-ff P</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>The --no-ff option creates a new branch A'-B'-C' with all-new commits (all the
|
|
SHA IDs will be different) even if in the interactive case you only actually
|
|
modify commit B. You can then merge this new branch directly into the mainline
|
|
branch and be sure you’ll get all of the branch’s changes.</p></div>
|
|
<div class="paragraph"><p>You can also use --no-ff in cases where you just add extra commits to the topic
|
|
to fix it up. Let’s revisit the situation discussed at the start of this howto:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>P---o---o---M---x---x---W---x
|
|
\ /
|
|
A---B---C----------------D---E <-- fixed-up topic branch</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>At this point, you can use --no-ff to recreate the topic branch:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code>$ git checkout E
|
|
$ git rebase --no-ff P</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>yielding</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code> A'---B'---C'------------D'---E' <-- recreated topic branch
|
|
/
|
|
P---o---o---M---x---x---W---x
|
|
\ /
|
|
A---B---C----------------D---E</code></pre>
|
|
</div></div>
|
|
<div class="paragraph"><p>You can merge the recreated branch into the mainline without reverting commit W,
|
|
and mainline’s history will look like this:</p></div>
|
|
<div class="literalblock">
|
|
<div class="content">
|
|
<pre><code> A'---B'---C'------------D'---E'
|
|
/ \
|
|
P---o---o---M---x---x---W---x---M2
|
|
\ /
|
|
A---B---C</code></pre>
|
|
</div></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div id="footnotes"><hr /></div>
|
|
<div id="footer">
|
|
<div id="footer-text">
|
|
Last updated
|
|
2025-08-29 17:49:33 CEST
|
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</div>
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</div>
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</body>
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</html>
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