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| author | Owen Jacobson <owen.jacobson@grimoire.ca> | 2015-07-03 22:31:49 -0400 |
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| committer | Owen Jacobson <owen.jacobson@grimoire.ca> | 2015-07-03 22:35:09 -0400 |
| commit | 76aed6ef732de38d82245b3d674f70bab30221e5 (patch) | |
| tree | d50e9a296d91ef8a49bcb29c3e80096f200a3c26 /.html/git/theory-and-practice/refs-and-names.html | |
| parent | 92f66d3e3a0996bb1fad9dc83d7e184f92673e5d (diff) | |
Fuck it, serve the files directly.
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| -rw-r--r-- | .html/git/theory-and-practice/refs-and-names.html | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/.html/git/theory-and-practice/refs-and-names.html b/.html/git/theory-and-practice/refs-and-names.html new file mode 100644 index 0000000..fdc56a4 --- /dev/null +++ b/.html/git/theory-and-practice/refs-and-names.html @@ -0,0 +1,199 @@ +<!DOCTYPE html> +<html> +<head> + <title> + The Codex » + Refs and Names + </title> + + <link + rel='stylesheet' + type='text/css' + href='http://fonts.googleapis.com/css?family=Buenard:400,700&subset=latin,latin-ext'> + <link + rel="stylesheet" + type="text/css" + href="../../media/css/reset.css"> + <link + rel="stylesheet" + type="text/css" + href="../../media/css/grimoire.css"> +</head> +<body> + +<div id="shell"> + + <ol id="breadcrumbs"> + + <li class="crumb-0 not-last"> + + <a href="../../">index</a> + + </li> + + <li class="crumb-1 not-last"> + + <a href="../">git</a> + + </li> + + <li class="crumb-2 not-last"> + + <a href="./">theory-and-practice</a> + + </li> + + <li class="crumb-3 last"> + + refs-and-names + + </li> + + </ol> + + + + <div id="article"> + <h1 id="refs-and-names">Refs and Names</h1> +<p>Git's <a href="objects">object system</a> stores most of the data for projects tracked in +Git, but only provides SHA-1 hashes. This is basically useless if you want to +make practical use of Git, so Git also has a naming mechanism called “refs” +that provide human-meaningful names for objects.</p> +<p>There are two kinds of refs:</p> +<ul> +<li> +<p>“Normal” refs, which are names that resolve directly to SHA-1 hashes. These + are the vast majority of refs in most repositories.</p> +</li> +<li> +<p>“Symbolic” refs, which are names that resolve to other refs. In most + repositories, only a few of these appear. (Circular references are possible + with symbolic refs. Git will refuse to resolve these.)</p> +</li> +</ul> +<p>Anywhere you could use a SHA-1, you can use a ref instead. Git interprets them +identically, after resolving the ref down to the SHA-1.</p> +<h2 id="namespaces">Namespaces</h2> +<p>Every operation in Git that uses a name of some sort, including branching +(branch names), tagging (tag names), fetching (remote-tracking branch names), +and pushing (many kinds of name), expands those names to refs, using a +namespace convention. The following namespaces are common:</p> +<ul> +<li> +<p><code>refs/heads/NAME</code>: branches. The branch name is the ref name with + <code>refs/heads/</code> removed. Names generally point to commits.</p> +</li> +<li> +<p><code>refs/remotes/REMOTE/NAME</code>: “remote-tracking” branches. These are maintained + in tandem by <code>git remote</code> and <code>git fetch</code>, to cache the state of other + repositories. Names generally point to commits.</p> +</li> +<li> +<p><code>refs/tags/NAME</code>: tags. The tag name is the ref name with <code>refs/heads/</code> + removed. Names generally point to commits or tag objects.</p> +</li> +<li> +<p><code>refs/bisect/STATE</code>: <code>git bisect</code> markers for known-good and known-bad + revisions, from which the rest of the bisect state can be derived.</p> +</li> +</ul> +<p>There are also a few special refs directly in the <code>refs/</code> namespace, most +notably:</p> +<ul> +<li><code>refs/stash</code>: The most recent stash entry, as maintained by <code>git stash</code>. + (Other stash entries are maintained by a separate system.) Names generally + point to commits.</li> +</ul> +<p>Tools can invent new refs for their own purposes, or manipulate existing refs; +the convention is that tools that use refs (which is, as I said, most of them) +respect the state of the ref as if they'd created that state themselves, +rather than sanity-checking the ref before using it.</p> +<h2 id="special-refs">Special refs</h2> +<p>There are a handful of special refs used by Git commands for their own +operation. These refs do <em>not</em> begin with <code>refs/</code>:</p> +<ul> +<li> +<p><code>HEAD</code>: the “current” commit for most operations. This is set when checking + out a commit, and many revision-related commands default to <code>HEAD</code> if not + given a revision to operate on. <code>HEAD</code> can either be a symbolic ref + (pointing to a branch ref) or a normal ref (pointing directly to a commit), + and is very frequently a symbolic ref.</p> +</li> +<li> +<p><code>MERGE_HEAD</code>: during a merge, <code>MERGE_HEAD</code> resolves to the commit whose + history is being merged.</p> +</li> +<li> +<p><code>ORIG_HEAD</code>: set by operations that change <code>HEAD</code> in potentially destructive + ways by resolving <code>HEAD</code> before making the change.</p> +</li> +<li> +<p><code>CHERRY_PICK_HEAD</code> is set during <code>git cherry-pick</code> to the commit whose + changes are being copied.</p> +</li> +<li> +<p><code>FETCH_HEAD</code> is set by the forms of <code>git fetch</code> that fetch a single ref, and + points to the commit the fetched ref pointed to.</p> +</li> +</ul> +<h2 id="examining-and-manipulating-refs">Examining and manipulating refs</h2> +<p>The <code>git show-ref</code> command will list the refs in namespaces under <code>refs</code> in +your repository, printing the SHA-1 hashes they resolve to. Pass <code>--head</code> to +also include <code>HEAD</code>.</p> +<p>The following commands can be used to manipulate refs directly:</p> +<ul> +<li> +<p><code>git update-ref <ref> <sha1></code> forcibly sets <code><ref></code> to the passed <code><sha1></code>.</p> +</li> +<li> +<p><code>git update-ref -d <ref></code> deletes a ref.</p> +</li> +<li> +<p><code>git symbolic-ref <ref></code> prints the target of <code><ref></code>, if <code><ref></code> is a + symbolic ref. (It will fail with an error message for normal refs.)</p> +</li> +<li> +<p><code>git symbolic-ref <ref> <target></code> forcibly makes <code><ref></code> a symbolic ref + pointing to <code><target></code>.</p> +</li> +</ul> +<p>Additionally, you can see what ref a given name resolves to using <code>git +rev-parse --symbolic-full-name <name></code> or <code>git show-ref <name></code>.</p> + </div> + + + +<div id="comments"> +<div id="disqus_thread"></div> +<script type="text/javascript"> + /* * * CONFIGURATION VARIABLES: EDIT BEFORE PASTING INTO YOUR WEBPAGE * * */ + var disqus_shortname = 'grimoire'; // required: replace example with your forum shortname + + /* * * DON'T EDIT BELOW THIS LINE * * */ + (function() { + var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true; + dsq.src = 'http://' + disqus_shortname + '.disqus.com/embed.js'; + (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq); + })(); +</script> +<noscript>Please enable JavaScript to view the <a href="http://disqus.com/?ref_noscript">comments powered by Disqus.</a></noscript> +<a href="http://disqus.com" class="dsq-brlink">comments powered by <span class="logo-disqus">Disqus</span></a> +</div> + + + + <div id="footer"> + <p> + + The Codex — + + Powered by <a href="http://markdoc.org/">Markdoc</a>. + +<a href="https://bitbucket.org/ojacobson/grimoire.ca/src/master/wiki/git/theory-and-practice/refs-and-names.md">See this page on Bitbucket</a> (<a href="https://bitbucket.org/ojacobson/grimoire.ca/history-node/master/wiki/git/theory-and-practice/refs-and-names.md">history</a>). + + </p> + </div> + +</div> +</body> +</html>
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