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  12 <title>cvs2git Documentation</title>
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  17
  18 <h1>cvs2git</h1>
  19
  20 <h2>Index</h2>
  21
  22 <ul>
  23
  24   <li><a href="#intro">Introduction</a></li>
  25
  26   <li><a href="#reqs">Requirements</a></li>
  27
  28   <li><a href="#status">Development status</a></li>
  29
  30   <li><a href="#docs">Documentation</a></li>
  31
  32   <li><a href="#usage">Usage</a></li>
  33
  34 </ul>
  35
  36 <hr />
  37
  38 <h2><a name="intro">Introduction</a></h2>
  39
  40 <p>cvs2svn/cvs2git is a tool that can be used to migrate CVS
  41 repositories to newer version control tools, including <a
  42 href="http://git.or.cz/">git</a>.  git is a distributed version
  43 control system most famous for being used for Linux kernel
  44 development.  The program used to convert to git, called cvs2git, is
  45 distributed as part of the cvs2svn project.</p>
  46
  47 <p><strong>If you are reading this documentation on the <a
  48 href="http://cvs2svn.tigris.org">cvs2svn website</a>, then please be
  49 aware that it describes the current trunk version of cvs2svn, which
  50 may be different than the most recent released version.  Please refer
  51 to the documentation that was included with your version of cvs2svn.
  52 </strong></p>
  53
  54 <p>Conversion to git was added in release 2.1 of cvs2svn and has
  55 improved significantly since then.  Please make sure you are using an
  56 up-to-date version of cvs2svn--perhaps even the development trunk
  57 version.</p>
  58
  59
  60 <h2><a name="reqs">Requirements</a></h2>
  61
  62 <p>cvs2git requires the following:</p>
  63
  64 <ul>
  65
  66   <li>Direct (filesystem) access to a copy of the CVS repository that
  67     you want to convert.  cvs2git parses the files in the CVS
  68     repository directly, so it is not enough to have remote CVS
  69     access.  See the <a href="faq.html#repoaccess">FAQ</a> for more
  70     information and a possible workaround.</li>
  71
  72   <li>Python 2, version 2.4 or later.  See <a
  73     href="http://www.python.org/">http://www.python.org/</a>.
  74     (cvs2git does <strong>not</strong> work with Python 3.x.)</li>
  75
  76   <li>If you use the <tt>--use-rcs</tt> option, then RCS's `co'
  77     program is required.  The RCS home page is
  78     <a href="http://www.cs.purdue.edu/homes/trinkle/RCS/"
  79             >http://www.cs.purdue.edu/homes/trinkle/RCS/</a>.
  80     See the <a href="cvs2svn.html#use-rcs"><tt>--use-rcs</tt> flag</a> for more
  81     details.</li>
  82
  83   <li>If you use the <tt>--use-cvs</tt> option, then the `cvs' command
  84     is required.  The CVS home page is
  85     <a href="http://ccvs.cvshome.org/">http://ccvs.cvshome.org/</a>.
  86     See the <a href="cvs2svn.html#use-cvs"><tt>--use-cvs</tt> flag</a> for more
  87     details.</li>
  88
  89   <li> Git version 1.5.4.4 or later (earlier versions have a bug in
  90     "git fast-import" that prevent them from loading the files
  91     generated by cvs2git).</li>
  92
  93 </ul>
  94
  95
  96 <h2><a name="status">Development status</a></h2>
  97
  98 <p>Most of the work of converting a repository from CVS to a more
  99 modern version control system is inferring the most likely history
 100 given the incomplete information that CVS records.  cvs2svn has a long
 101 history of making sense of even the most convoluted CVS repositories,
 102 and cvs2git uses this same machinery.  Therefore, cvs2git inherits the
 103 robustness and many of the <a href="features.html">features of
 104 cvs2svn</a>.  cvs2svn can convert just about every CVS repository we
 105 have ever seen, and includes a plethora of options for customizing
 106 your conversion.</p>
 107
 108 <p>The output of cvs2git is one or more dump files that can be
 109 imported into git using the excellent <a
 110 href="http://www.kernel.org/pub/software/scm/git/docs/git
 111 fast-import.html">git fast-import</a> tool.</p>
 112
 113 <p>Although cvs2git is considerably newer than cvs2svn, and much less
 114 well tested, it is believed that cvs2git can (cautiously) be used for
 115 production conversions.  If you use cvs2git, please let us know how it
 116 worked for you!</p>
 117
 118
 119 <h2><a name="limitations">cvs2git limitations</a></h2>
 120
 121 <p>cvs2git still has many limitations compared to cvs2svn.  The main
 122 cvs2svn developer has limited git experience and very limited time, so
 123 <strong>help would be much appreciated!</strong> Some of these missing
 124 features would be pretty easy to program, and I'd be happy to help you
 125 get started.</p>
 126
 127 <ul>
 128
 129   <li>The cvs2git documentation is still rather thin.  See <a
 130     href="#docs">below</a> for more references.</li>
 131
 132   <li>CVS allows a branch to be created from arbitrary combinations of
 133     source revisions and/or source branches.  cvs2git tries to create
 134     a branch from a single source, but if it can't figure out how to,
 135     it creates the branch using "merge" from multiple sources.  In
 136     pathological situations, the number of merge sources for a branch
 137     can be arbitrarily large.</li>
 138
 139   <li>If cvs2git cannot determine that a CVS tag can be created from a
 140     single revision, then it creates a <a
 141     href="http://www.kernel.org/pub/software/scm/git/docs/git-fast-import.html">tag
 142     fixup branch</a> named <tt>TAG.FIXUP</tt>, then tags this branch.
 143     (This is a necessary workaround for the fact that CVS tags are
 144     fundamentally different than git tags.)  The <tt>TAG.FIXUP</tt>
 145     branch is cleared at the end of the conversion, but not deleted.
 146     There are some situations when a tag <em>could</em> be created
 147     from a single revision, but cvs2git does not realize it and
 148     creates a superfluous tag fixup branch.  It is possible to delete
 149     all superfluous tag fixup branches after the conversion, by
 150     running the <tt>contrib/git-move-refs.py</tt> script within the
 151     resulting git repository.</li>
 152
 153   <li>There are no checks that CVS branch and tag names are legal git
 154     names.  There are probably other git constraints that should also
 155     be checked.</li>
 156
 157   <li>The data that should be fed to git fast-import are written to
 158     two files, which have to be loaded into git fast-import manually.
 159     These files might grow to very large size.  It would be nice to
 160     add an option to invoke git fast-import automatically and pipe the
 161     output directly into git fast-import; this should also speed up
 162     the conversion.</li>
 163
 164   <li>Only single projects can be converted at a time.  Given the way
 165     git is typically used, I don't think that this is a significant
 166     limitation.</li>
 167
 168   <li>cvs2git is rather slow when started with the <tt>--use-rcs</tt>
 169     or <tt>--use-cvs</tt> options.  It is much faster when started
 170     with the <tt>--use-external-blob-generator</tt> option, but that
 171     option is still experimental.</li>
 172
 173   <li>The cvs2svn test suite does not include meaningful tests of git
 174     output.</li>
 175
 176   <li>cvs2git makes no attempt to convert <tt>.cvsignore</tt> files
 177     into <tt>.gitignore</tt> files.</li>
 178
 179   <li>cvs2git, like cvs2svn, does not support incremental conversion
 180     (i.e., tracking a live CVS repository).  However, at least one
 181     person has documented a <a
 182     href="http://www.oak.homeunix.org/~marcel/blog/2009/06/03/tracking-cvs-with-git-using-cvs2git">possible
 183     workaround</a>.</li>
 184
 185 </ul>
 186
 187
 188 <h2><a name="docs">Documentation</a></h2>
 189
 190 <p>There is some documentation specific to cvs2git, and much of the
 191 cvs2svn documentation also applies fairly straightforwardly to
 192 cvs2git.  See the following sources:</p>
 193
 194 <ul>
 195
 196   <li>This document.</li>
 197
 198   <li>The cvs2git man page and the output of <tt>cvs2git
 199     --help</tt>.</li>
 200
 201   <li><a href="cvs2svn.html#intro">The cvs2svn documentation</a> and
 202     <a href="faq.html">the cvs2svn FAQ</a>, which contain much general
 203     discussion and describe many features that can also be used for
 204     cvs2git.</li>
 205
 206   <li><tt>cvs2git-example.options</tt> in the cvs2svn source tree,
 207     which is an example of an options file that can be used to
 208     configure a cvs2git conversion.  The file is extensively
 209     documented.</li>
 210
 211   <li>The cvs2svn mailing lists, IRC channel, etc., as described in <a
 212     href="faq.html#gettinghelp">the cvs2svn FAQ</a>.</li>
 213
 214 </ul>
 215
 216
 217 <h2><a name="usage">Usage</a></h2>
 218
 219 <p>This section outlines the steps needed to convert a CVS repository
 220 to git using cvs2git.</p>
 221
 222 <ol>
 223
 224   <li>Be sure that you have the <a href="#reqs">requirements</a>,
 225     including either RCS or CVS (used to read revision contents from
 226     the CVS repository).</li>
 227
 228   <li>Obtain a copy of cvs2svn/cvs2git version 2.1 or newer.  It is
 229     recommended that you use the most recent version available, or
 230     even the development version.
 231
 232     <ul>
 233
 234       <li>To install cvs2svn from a <a
 235         href="http://cvs2svn.tigris.org/servlets/ProjectDocumentList">tarball</a>,
 236         simply unpack the tarball into a directory on your conversion
 237         computer (cvs2git can be run directly from this
 238         directory).</li>
 239
 240       <li>
 241
 242         <p>To check out the current trunk version of cvs2svn, make
 243           sure that you have Subversion installed and then run:</p>
 244
 245 <pre>
 246 svn co --username=guest http://cvs2svn.tigris.org/svn/cvs2svn/trunk cvs2svn-trunk
 247 # The password is empty; i.e., just press return.
 248 cd cvs2svn-trunk
 249 make man # If you want to create manpages for the main programs
 250 make check # ...optional
 251 </pre>
 252
 253         <p>Please note that the test suite includes tests that are
 254           marked "XFAIL" (expected failure); these are known and are
 255           not considered serious problems.</p>
 256
 257       </li>
 258
 259     </ul>
 260
 261   </li>
 262
 263   <li>
 264
 265     Configure cvs2git for your conversion.  This can be done via
 266     command-line options or via an options file:
 267
 268     <ul>
 269
 270       <li>The command-line options for running cvs2git are documented
 271         in the cvs2git man page and in the output of <tt>cvs2git
 272         --help</tt>.</li>
 273
 274       <li>
 275
 276         <p>The more flexible <a
 277           href="cvs2svn.html#cmd-vs-options">options-file method</a>
 278           requires you to create an options file, then start cvs2git
 279           with</p>
 280
 281 <pre>
 282 cvs2git --options=OPTIONS-FILE
 283 </pre>
 284
 285         <p>Use <tt>cvs2git-example.options</tt> in the cvs2svn source
 286           tree as your starting point; the file contains lots of
 287           documentation.</p>
 288
 289       </li>
 290
 291     </ul>
 292
 293   </li>
 294
 295   <li>
 296
 297     <p>Run cvs2git.  This creates two output files in <a
 298     href="http://www.kernel.org/pub/software/scm/git/docs/git-fast-import.html">git
 299     fast-import</a> format.  The names of these files are specified by
 300     your options file or command-line arguments.  In the example,
 301     these files are named <tt>cvs2svn-tmp/git-blob.dat</tt> and
 302     <tt>cvs2svn-tmp/git-dump.dat</tt>.</p>
 303
 304   </li>
 305
 306   <li>
 307
 308     <p>Initialize a git repository, and load the dump files using
 309       git fast-import:</p>
 310
 311 <pre>
 312 git init
 313 cat cvs2svn-tmp/git-blob.dat | git fast-import --export-marks=cvs2svn-tmp/git-marks.dat
 314 cat cvs2svn-tmp/git-dump.dat | git fast-import --import-marks=cvs2svn-tmp/git-marks.dat
 315 </pre>
 316
 317     <p>This can, of course, be shortened to:</p>
 318
 319 <pre>
 320 git init
 321 cat cvs2svn-tmp/git-blob.dat cvs2svn-tmp/git-dump.dat | git fast-import
 322 </pre>
 323
 324   </li>
 325
 326   <li>If you want to get rid of unnecessary tag fixup branches, then
 327     run the <tt>contrib/git-move-refs.py</tt> script from within the
 328     git repository.</li>
 329
 330 </ol>
 331
 332 <p>Feedback would be much appreciated, including reports of success
 333   using cvs2git.  Please send comments, bug reports, and patches to
 334   the <a
 335   href="http://cvs2svn.tigris.org/servlets/ProjectMailingListList">cvs2svn
 336   mailing lists</a>.</p>
 337
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