<?xml version="1.0" encoding="utf-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Traversing Branches</title> <link rel="stylesheet" type="text/css" href="styles.css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /> <style type="text/css"> body { background-image: url('images/draft.png'); background-repeat: no-repeat; background-position: top left; /* The following properties make the watermark "fixed" on the page. */ /* I think that's just a bit too distracting for the reader... */ /* background-attachment: fixed; */ /* background-position: center center; */ }</style> <link rel="home" href="index.html" title="Version Control with Subversion [DRAFT]" /> <link rel="up" href="svn.branchmerge.html" title="Chapter 4. Branching and Merging" /> <link rel="prev" href="svn.branchmerge.advanced.html" title="Advanced Merging" /> <link rel="next" href="svn.branchmerge.tags.html" title="Tags" /> </head> <body> <div xmlns="" id="vcws-version-notice"> <p>This text is a work in progress—highly subject to change—and may not accurately describe any released version of the Apache™ Subversion® software. Bookmarking or otherwise referring others to this page is probably not such a smart idea. Please visit <a href="http://www.svnbook.com/">http://www.svnbook.com/</a> for stable versions of this book.</p> </div> <div class="navheader"> <table width="100%" summary="Navigation header"> <tr> <th colspan="3" align="center">Traversing Branches</th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="svn.branchmerge.advanced.html">Prev</a> </td> <th width="60%" align="center">Chapter 4. Branching and Merging</th> <td width="20%" align="right"> <a accesskey="n" href="svn.branchmerge.tags.html">Next</a></td> </tr> </table> <hr /> </div> <div class="sect1"> <div class="titlepage"> <div> <div> <h2 class="title" style="clear: both"><a id="svn.branchmerge.switchwc"></a>Traversing Branches</h2> </div> </div> </div> <p>The <span class="command"><strong>svn switch</strong></span> command transforms an existing working copy to reflect a different branch. While this command isn't strictly necessary for working with branches, it provides a nice shortcut. In one of our earlier examples, after creating your private branch, you checked out a fresh working copy of the new repository directory. Instead, you can simply ask Subversion to change your working copy of <code class="filename">/calc/trunk</code> to mirror the new branch location:</p> <div class="informalexample"> <pre class="screen"> $ cd calc $ svn info | grep URL URL: http://svn.example.com/repos/calc/trunk Relative URL: ^/calc/trunk $ svn switch ^/calc/branches/my-calc-branch U integer.c U button.c U Makefile Updated to revision 341. $ svn info | grep URL URL: http://svn.example.com/repos/calc/branches/my-calc-branch Relative URL: ^/calc/branches/my-calc-branch $ </pre> </div> <p><span class="quote">“<span class="quote">Switching</span>”</span> a working copy that has no local modifications to a different branch results in the working copy looking just as it would if you'd done a fresh checkout of the directory. It's usually more efficient to use this command, because often branches differ by only a small degree. The server sends only the minimal set of changes necessary to make your working copy reflect the branch directory.</p> <p>The <span class="command"><strong>svn switch</strong></span> command also takes a <code class="option">--revision</code> (<code class="option">-r</code>) option, so you need not always move your working copy to the <code class="literal">HEAD</code> of the branch.</p> <p>Of course, most projects are more complicated than our <code class="filename">calc</code> example, and contain multiple subdirectories. Subversion users often follow a specific algorithm when using branches:</p> <div class="orderedlist"> <ol class="orderedlist" type="1"> <li class="listitem"> <p>Copy the project's entire <span class="quote">“<span class="quote">trunk</span>”</span> to a new branch directory.</p> </li> <li class="listitem"> <p>Switch only <span class="emphasis"><em>part</em></span> of the trunk working copy to mirror the branch.</p> </li> </ol> </div> <p>In other words, if a user knows that the branch work needs to happen on only a specific subdirectory, she uses <span class="command"><strong>svn switch</strong></span> to move only that subdirectory to the branch. (Or sometimes users will switch just a single working file to the branch!) That way, the user can continue to receive normal <span class="quote">“<span class="quote">trunk</span>”</span> updates to most of her working copy, but the switched portions will remain immune (unless someone commits a change to her branch). This feature adds a whole new dimension to the concept of a <span class="quote">“<span class="quote">mixed working copy</span>”</span>—not only can working copies contain a mixture of working revisions, but they can also contain a mixture of repository locations as well.</p> <div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"> <table border="0" summary="Tip"> <tr> <td rowspan="2" align="center" valign="top" width="25"> <img alt="[Tip]" src="images/tip.png" /> </td> <th align="left">Tip</th> </tr> <tr> <td align="left" valign="top"> <p>Typically switched subdirectories share common ancestry with the location which is switched <span class="quote">“<span class="quote">away</span>”</span> from. However <span class="command"><strong>svn switch</strong></span> can switch a subdirectory to mirror a repository location which it shares no common ancestry with. To do this you need to use the <code class="option">--ignore-ancestry</code> option. </p> </td> </tr> </table> </div> <p>If your working copy contains a number of switched subtrees from different repository locations, it continues to function as normal. When you update, you'll receive patches to each subtree as appropriate. When you commit, your local changes are still applied as a single, atomic change to the repository.</p> <p>Note that while it's okay for your working copy to reflect a mixture of repository locations, these locations must all be within the <span class="emphasis"><em>same</em></span> repository. Subversion repositories aren't yet able to communicate with one another; that feature is planned for the future.<a href="#ftn.idm5535" class="footnote" id="idm5535"><sup class="footnote">[43]</sup></a></p> <div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"> <table border="0" summary="Tip"> <tr> <td rowspan="2" align="center" valign="top" width="25"> <img alt="[Tip]" src="images/tip.png" /> </td> <th align="left">Tip</th> </tr> <tr> <td align="left" valign="top"> <p>Administrators who need to change the URL of a repository which is accessed via HTTP are encouraged to add to their <code class="filename">httpd.conf</code> configuration file a permanent redirect from the old URL location to the new one (via the <code class="literal">RedirectPermanent</code> directive). Subversion clients will generally display the new repository URL in error messages generated when the user attempts to use working copies which still reflect the old URL location. Since Subversion 1.7 clients will go a step further, automatically relocating the working copy to the new URL.</p> </td> </tr> </table> </div> <div class="sidebar"> <div class="titlepage"> <div> <div> <p class="title"> <strong>Switches and Updates</strong> </p> </div> </div> </div> <p>Have you noticed that the output of <span class="command"><strong>svn switch</strong></span> and <span class="command"><strong>svn update</strong></span> looks the same? The switch command is actually a superset of the update command.</p> <p>When you run <span class="command"><strong>svn update</strong></span>, you're asking the repository to compare two trees. The repository does so, and then sends a description of the differences back to the client. The only difference between <span class="command"><strong>svn switch</strong></span> and <span class="command"><strong>svn update</strong></span> is that the latter command always compares two identical repository paths.</p> <p>That is, if your working copy is a mirror of <code class="filename">/calc/trunk</code>, <span class="command"><strong>svn update</strong></span> will automatically compare your working copy of <code class="filename">/calc/trunk</code> to <code class="filename">/calc/trunk</code> in the <code class="literal">HEAD</code> revision. If you're switching your working copy to a branch, <span class="command"><strong>svn switch</strong></span> will compare your working copy of <code class="filename">/calc/trunk</code> to some <span class="emphasis"><em>other</em></span> branch directory in the <code class="literal">HEAD</code> revision.</p> <p>In other words, an update moves your working copy through time. A switch moves your working copy through time <span class="emphasis"><em>and</em></span> space.</p> </div> <p>Because <span class="command"><strong>svn switch</strong></span> is essentially a variant of <span class="command"><strong>svn update</strong></span>, it shares the same behaviors; any local modifications in your working copy are preserved when new data arrives from the repository.</p> <div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"> <table border="0" summary="Tip"> <tr> <td rowspan="2" align="center" valign="top" width="25"> <img alt="[Tip]" src="images/tip.png" /> </td> <th align="left">Tip</th> </tr> <tr> <td align="left" valign="top"> <p>Have you ever found yourself making some complex edits (in your <code class="filename">/trunk</code> working copy) and suddenly realized, <span class="quote">“<span class="quote">Hey, these changes ought to be in their own branch?</span>”</span> There is a great two step technique to do this:</p> <div class="informalexample"> <pre class="screen"> $ svn copy http://svn.example.com/repos/calc/trunk \ http://svn.example.com/repos/calc/branches/newbranch \ -m "Create branch 'newbranch'." Committed revision 353. $ svn switch ^/calc/branches/newbranch At revision 353. </pre> </div> <p>The <span class="command"><strong>svn switch</strong></span> command, like <span class="command"><strong>svn update</strong></span>, preserves your local edits. At this point, your working copy is now a reflection of the newly created branch, and your next <span class="command"><strong>svn commit</strong></span> invocation will send your changes there.</p> </td> </tr> </table> </div> <div class="footnotes"> <br /> <hr style="width:100; text-align:left;margin-left: 0" /> <div id="ftn.idm5535" class="footnote"> <p><a href="#idm5535" class="para"><sup class="para">[43] </sup></a>You <span class="emphasis"><em>can</em></span>, however, use <span class="command"><strong>svn relocate</strong></span> if the URL of your server changes and you don't want to abandon an existing working copy. See <a class="xref" href="svn.ref.svn.c.relocate.html" title="svn relocate">svn relocate</a> in <a class="xref" href="svn.ref.svn.html" title="svn Reference—Subversion Command-Line Client">svn Reference—Subversion Command-Line Client</a> for more information and an example.</p> </div> </div> </div> <div class="navfooter"> <hr /> <table width="100%" summary="Navigation footer"> <tr> <td width="40%" align="left"><a accesskey="p" href="svn.branchmerge.advanced.html">Prev</a> </td> <td width="20%" align="center"> <a accesskey="u" href="svn.branchmerge.html">Up</a> </td> <td width="40%" align="right"> <a accesskey="n" href="svn.branchmerge.tags.html">Next</a></td> </tr> <tr> <td width="40%" align="left" valign="top">Advanced Merging </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> <td width="40%" align="right" valign="top"> Tags</td> </tr> </table> </div> <div xmlns="" id="vcws-footer"> <hr /> <img src="images/cc-by.png" style="float: right;" /> <p>You are reading <em>Version Control with Subversion</em> (for Subversion 1.8), by Ben Collins-Sussman, Brian W. Fitzpatrick, and C. Michael Pilato.</p> <p>This work is licensed under the <a href="http://creativecommons.org/licenses/by/2.0/">Creative Commons Attribution License v2.0</a>.</p> <p>To submit comments, corrections, or other contributions to the text, please visit <a href="http://www.svnbook.com/">http://www.svnbook.com/</a>.</p> </div> </body> </html>