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Diffstat (limited to '.html/git/theory-and-practice')
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| -rw-r--r-- | .html/git/theory-and-practice/index.html | 126 | ||||
| -rw-r--r-- | .html/git/theory-and-practice/objects.html | 202 | ||||
| -rw-r--r-- | .html/git/theory-and-practice/refs-and-names.html | 199 |
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diff --git a/.html/git/theory-and-practice/_list.html b/.html/git/theory-and-practice/_list.html deleted file mode 100644 index feae190..0000000 --- a/.html/git/theory-and-practice/_list.html +++ /dev/null @@ -1,96 +0,0 @@ -<!DOCTYPE html> -<html> -<head> - <title> - The Codex » - ls /git/theory-and-practice - </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"> - - <span class="list-crumb">list</span> - - </li> - - </ol> - - - - <div id="listing"> - <h1><code>ls /git/theory-and-practice</code></h1> - - - - - <div id="pages"> - <h2>Pages</h2> - <ul> - - <li><a href="objects">Objects</a></li> - - <li><a href="refs-and-names">Refs and Names</a></li> - - </ul> - </div> - - - - </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">See this directory on Bitbucket</a>. - - </p> - </div> - -</div> -</body> -</html>
\ No newline at end of file diff --git a/.html/git/theory-and-practice/index.html b/.html/git/theory-and-practice/index.html deleted file mode 100644 index 297cbd9..0000000 --- a/.html/git/theory-and-practice/index.html +++ /dev/null @@ -1,126 +0,0 @@ -<!DOCTYPE html> -<html> -<head> - <title> - The Codex » - Git Internals 101 - </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 last"> - - theory-and-practice - - </li> - - </ol> - - - - <div id="article"> - <h1 id="git-internals-101">Git Internals 101</h1> -<p>Yeah, yeah, another article about “how Git works.” There are tons of these -already. Personally, I'm fond of Sitaram Chamarty's <a href="http://gitolite.com/master-toc.html">fantastic series of -articles</a> explaining Git from both ends, -and of <a href="http://eagain.net/articles/git-for-computer-scientists/">Git for Computer -Scientists</a>. Maybe -you'd rather read those.</p> -<p>This page was inspired by very specific, recurring issues I've run into while -helping people use Git. I think Git's “porcelain” layer -- its user interface --- is terrible, and does a bad job of insulating non-expert users from Git's -internals. While I'd love to fix that (and I do contribute to discussions on -that front, too), we still have the <code>git(1)</code> UI right now and people still get -into trouble with it right now.</p> -<p>Git follows the New Jersey approach laid out in Richard Gabriel's <a href="http://www.dreamsongs.com/RiseOfWorseIsBetter.html">The Rise of -“Worse is Better”</a>: given -the choice between a simple implementation and a simple interface, Git chooses -the simple implementation almost everywhere. This internal simplicity can give -users the leverage to fix the problems that its horrible user interface leads -them into, so these pages will focus on explaining the simple parts and giving -users the tools to examine them.</p> -<p>Throughout these articles, I've written “Git does X” a lot. Git is -<em>incredibly</em> configurable; read that as “Git does X <em>by default</em>.” I'll try to -call out relevant configuration options as I go, where it doesn't interrupt -the flow of knowledge.</p> -<ul> -<li><a href="objects">Objects</a></li> -<li><a href="refs-and-names">Refs and Names</a></li> -</ul> -<p>By the way, if you think you're just going to follow the -<a href="http://git-scm.com/documentation">many</a> -<a href="http://www.atlassian.com/git/tutorial">excellent</a> -<a href="http://try.github.io/levels/1/challenges/1">git</a> -<a href="https://www.kernel.org/pub/software/scm/git/docs/gittutorial.html">tutorials</a> -out there and that you won't need this knowledge, well, you will. You can -either learn it during a quiet time, when you can think and experiment, or you -can learn it when something's gone wrong, and everyone's shouting at each -other. Git's high-level interface doesn't do much to keep you on the sensible -path, and you will eventually need to fix something.</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/index.md">See this page on Bitbucket</a> (<a href="https://bitbucket.org/ojacobson/grimoire.ca/history-node/master/wiki/git/theory-and-practice/index.md">history</a>). - - </p> - </div> - -</div> -</body> -</html>
\ No newline at end of file diff --git a/.html/git/theory-and-practice/objects.html b/.html/git/theory-and-practice/objects.html deleted file mode 100644 index ff6c53b..0000000 --- a/.html/git/theory-and-practice/objects.html +++ /dev/null @@ -1,202 +0,0 @@ -<!DOCTYPE html> -<html> -<head> - <title> - The Codex » - Objects - </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"> - - objects - - </li> - - </ol> - - - - <div id="article"> - <h1 id="objects">Objects</h1> -<p>Git's basest level is a storage and naming system for things Git calls -“objects.” These objects hold the bulk of the data about files and projects -tracked by Git: file contents, directory trees, commits, and so on. Every -object is identified by a SHA-1 hash, which is derived from its contents.</p> -<p>SHA-1 hashes are obnoxiously long, so Git allows you to substitue any unique -prefix of a SHA-1 hash, so long as it's at least four characters long. If the -hash <code>0b43b9e3e64793f5a222a644ed5ab074d8fa1024</code> is present in your repository, -then Git commands will understand <code>0b43</code>, <code>0b43b9</code>, and other patterns to all -refer to the same object, so long as no other object has the same SHA-1 -prefix.</p> -<h2 id="blobs">Blobs</h2> -<p>The contents of every file that's ever been stored in a Git repository are -stored as <code>blob</code> objects. These objects are very simple: they contain the file -contents, byte for byte.</p> -<h2 id="trees">Trees</h2> -<p>File contents (and trees, and Other Things we'll get to later) are tied -together into a directory structure by <code>tree</code> objects. These objects contain a -list of records, with one child per record. Each record contains a permissions -field corresponding to the POSIX permissions mask of the object, a type, a -SHA-1 for another object, and a name.</p> -<p>A directory containing only files might be represented as the tree</p> -<pre><code>100644 blob 511542ad6c97b28d720c697f7535897195de3318 config.md -100644 blob 801ddd5ae10d6282bbf36ccefdd0b052972aa8e2 integrate.md -100644 blob 61d28155862607c3d5d049e18c5a6903dba1f85e scratch.md -100644 blob d7a79c144c22775239600b332bfa120775bab341 survival.md -</code></pre> -<p>while a directory with subdirectories would also have some <code>tree</code> children:</p> -<pre><code>040000 tree f57ef2457a551b193779e21a50fb380880574f43 12factor -040000 tree 844697ce99e1ef962657ce7132460ad7a38b7584 authnz -100644 blob 54795f9b774547d554f5068985bbc6df7b128832 cool-urls-can-change.md -040000 tree fc3f39eb5d1a655374385870b8be56b202be7dd8 dev -040000 tree 22cbfb2c1d7b07432ea7706c36b0d6295563c69c devops -040000 tree 0b3e63b4f32c0c3acfbcf6ba28d54af4c2f0d594 git -040000 tree 5914fdcbd34e00e23e52ba8e8bdeba0902941d3f java -040000 tree 346f71a637a4f8933dc754fef02515a8809369c4 mysql -100644 blob b70520badbb8de6a74b84788a7fefe64a432c56d packaging-ideas.md -040000 tree 73ed6572345a368d20271ec5a3ffc2464ac8d270 people -</code></pre> -<h2 id="commits">Commits</h2> -<p>Blobs and trees are sufficient to store arbitrary directory trees in Git, and -you could use them that way, but Git is mostly used as a revision-tracking -system. Revisions and their history are represented by <code>commit</code> objects, which contain:</p> -<pre><code>* The SHA-1 hash of the root `tree` object of the commit, -* Zero or more SHA-1 hashes for parent commits, -* The name and email address of the commit's “author,” -* The name and email address of the commit's “committer,” -* Timestamps representing when the commit was authored and committed, and -* A commit message. -</code></pre> -<p>Commit objects' parent references form a directed acyclic graph; the subgraph -reachable from a specific commit is that commit's <em>history</em>.</p> -<p>When working with Git's user interface, commit parents are given in a -predictable order determined by the <code>git checkout</code> and <code>git merge</code> commands.</p> -<h2 id="tags">Tags</h2> -<p>Git's revision-tracking system supports “tags,” which are stable names for -specific configurations. It also, uniquely, supports a concept called an -“annotated tag,” represented by the <code>tag</code> object type. These annotated tag -objects contain</p> -<pre><code>* The type and SHA-1 hash of another object, -* The name and email address of the person who created the tag, -* A timestamp representing the moment the tag was created, and -* A tag message. -</code></pre> -<h2 id="anonymity">Anonymity</h2> -<p>There's a general theme to Git's object types: no object knows its own name. -Every object only has a name in the context of some containing object, or in -the context of <a href="refs-and-names">Git's refs mechanism</a>, which I'll get to -shortly. This means that the same <code>blob</code> object can be reused for multiple -files (or, more probably, the same file in multiple commits), if they happen -to have the same contents.</p> -<p>This also applies to tag objects, even though their role is part of a system -for providing stable, meaningful names for commits.</p> -<h2 id="examining-objects">Examining objects</h2> -<ul> -<li> -<p><code>git cat-file <type> <sha1></code>: decodes the object <code><sha1></code> and prints its - contents to stdout. This prints the object's contents in their raw form, - which is less than useful for <code>tree</code> objects.</p> -</li> -<li> -<p><code>git cat-file -p <sha1></code>: decodes the object <code><sha1></code> and pretty-prints it. - This pretty-printing stays close to the underlying disk format; it's most - useful for decoding <code>tree</code> objects.</p> -</li> -<li> -<p><code>git show <sha1></code>: decodes the object <code><sha1></code> and formats its contents to - stdout. For blobs, this is identical to what <code>git cat-file blob</code> would do, - but for trees, commits, and tags, the output is reformated to be more - readable.</p> -</li> -</ul> -<h2 id="storage">Storage</h2> -<p>Objects are stored in two places in Git: as “loose objects,” and in “pack -files.” Newly-created objects are initially loose objects, for ease of -manipulation; transferring objects to another repository or running certain -administrative commands can cause them to be placed in pack files for faster -transfer and for smaller storage.</p> -<p>Loose objects are stored directly on the filesystem, in the Git repository's -<code>objects</code> directory. Git takes a two-character prefix off of each object's -SHA-1 hash, and uses that to pick a subdirectory of <code>objects</code> to store the -object in. The remainder of the hash forms the filename. Loose objects are -compressed with zlib, to conserve space, but the resulting directory tree can -still be quite large.</p> -<p>Packed objects are stored together in packed files, which live in the -repository's <code>objects/pack</code> directory. These packed files are both compressed -and delta-encoded, allowing groups of similar objects to be stored very -compactly.</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/objects.md">See this page on Bitbucket</a> (<a href="https://bitbucket.org/ojacobson/grimoire.ca/history-node/master/wiki/git/theory-and-practice/objects.md">history</a>). - - </p> - </div> - -</div> -</body> -</html>
\ No newline at end of file diff --git a/.html/git/theory-and-practice/refs-and-names.html b/.html/git/theory-and-practice/refs-and-names.html deleted file mode 100644 index fdc56a4..0000000 --- a/.html/git/theory-and-practice/refs-and-names.html +++ /dev/null @@ -1,199 +0,0 @@ -<!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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