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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 not especially fast.  Among other things, it still
 169     uses RCS or CVS to extract the contents of the CVS revisions.
 170     Implementing the <tt>--internal-co</tt> option for cvs2git (using
 171     code that already exists in cvs2svn) might improve the conversion
 172     speed considerably.</li>
 173
 174   <li>The cvs2svn test suite does not include meaningful tests of git
 175     output.</li>
 176
 177   <li>cvs2git makes no attempt to convert <tt>.cvsignore</tt> files
 178     into <tt>.gitignore</tt> files.</li>
 179
 180   <li>cvs2git, like cvs2svn, does not support incremental conversion
 181     (i.e., tracking a live CVS repository).  However, at least one
 182     person has documented a <a
 183     href="http://www.oak.homeunix.org/~marcel/blog/2009/06/03/tracking-cvs-with-git-using-cvs2git">possible
 184     workaround</a>.</li>
 185
 186 </ul>
 187
 188
 189 <h2><a name="docs">Documentation</a></h2>
 190
 191 <p>There is some documentation specific to cvs2git, and much of the
 192 cvs2svn documentation also applies fairly straightforwardly to
 193 cvs2git.  See the following sources:</p>
 194
 195 <ul>
 196
 197   <li>This document.</li>
 198
 199   <li>The cvs2git man page and the output of <tt>cvs2git
 200     --help</tt>.</li>
 201
 202   <li><a href="cvs2svn.html#intro">The cvs2svn documentation</a> and
 203     <a href="faq.html">the cvs2svn FAQ</a>, which contain much general
 204     discussion and describe many features that can also be used for
 205     cvs2git.</li>
 206
 207   <li><tt>cvs2git-example.options</tt> in the cvs2svn source tree,
 208     which is an example of an options file that can be used to
 209     configure a cvs2git conversion.  The file is extensively
 210     documented.</li>
 211
 212   <li>The cvs2svn mailing lists, IRC channel, etc., as described in <a
 213     href="faq.html#gettinghelp">the cvs2svn FAQ</a>.</li>
 214
 215 </ul>
 216
 217
 218 <h2><a name="usage">Usage</a></h2>
 219
 220 <p>This section outlines the steps needed to convert a CVS repository
 221 to git using cvs2git.</p>
 222
 223 <ol>
 224
 225   <li>Be sure that you have the <a href="#reqs">requirements</a>,
 226     including either RCS or CVS (used to read revision contents from
 227     the CVS repository).</li>
 228
 229   <li>Obtain a copy of cvs2svn/cvs2git version 2.1 or newer.  It is
 230     recommended that you use the most recent version available, or
 231     even the development version.
 232
 233     <ul>
 234
 235       <li>To install cvs2svn from a <a
 236         href="http://cvs2svn.tigris.org/servlets/ProjectDocumentList">tarball</a>,
 237         simply unpack the tarball into a directory on your conversion
 238         computer (cvs2git can be run directly from this
 239         directory).</li>
 240
 241       <li>
 242
 243         <p>To check out the current trunk version of cvs2svn, make
 244           sure that you have Subversion installed and then run:</p>
 245
 246 <pre>
 247 svn co --username=guest http://cvs2svn.tigris.org/svn/cvs2svn/trunk cvs2svn-trunk
 248 # The password is empty; i.e., just press return.
 249 cd cvs2svn-trunk
 250 make man # If you want to create manpages for the main programs
 251 make check # ...optional
 252 </pre>
 253
 254         <p>Please note that the test suite includes tests that are
 255           marked "XFAIL" (expected failure); these are known and are
 256           not considered serious problems.</p>
 257
 258       </li>
 259
 260     </ul>
 261
 262   </li>
 263
 264   <li>
 265
 266     Configure cvs2git for your conversion.  This can be done via
 267     command-line options or via an options file:
 268
 269     <ul>
 270
 271       <li>The command-line options for running cvs2git are documented
 272         in the cvs2git man page and in the output of <tt>cvs2git
 273         --help</tt>.</li>
 274
 275       <li>
 276
 277         <p>The more flexible <a
 278           href="cvs2svn.html#cmd-vs-options">options-file method</a>
 279           requires you to create an options file, then start cvs2git
 280           with</p>
 281
 282 <pre>
 283 cvs2git --options=OPTIONS-FILE
 284 </pre>
 285
 286         <p>Use <tt>cvs2git-example.options</tt> in the cvs2svn source
 287           tree as your starting point; the file contains lots of
 288           documentation.</p>
 289
 290       </li>
 291
 292     </ul>
 293
 294   </li>
 295
 296   <li>
 297
 298     <p>Run cvs2git.  This creates two output files in <a
 299     href="http://www.kernel.org/pub/software/scm/git/docs/git-fast-import.html">git
 300     fast-import</a> format.  The names of these files are specified by
 301     your options file or command-line arguments.  In the example,
 302     these files are named <tt>cvs2svn-tmp/git-blob.dat</tt> and
 303     <tt>cvs2svn-tmp/git-dump.dat</tt>.</p>
 304
 305   </li>
 306
 307   <li>
 308
 309     <p>Initialize a git repository, and load the dump files using
 310       git fast-import:</p>
 311
 312 <pre>
 313 git init
 314 cat cvs2svn-tmp/git-blob.dat | git fast-import --export-marks=cvs2svn-tmp/git-marks.dat
 315 cat cvs2svn-tmp/git-dump.dat | git fast-import --import-marks=cvs2svn-tmp/git-marks.dat
 316 </pre>
 317
 318     <p>This can, of course, be shortened to:</p>
 319
 320 <pre>
 321 git init
 322 cat cvs2svn-tmp/git-blob.dat cvs2svn-tmp/git-dump.dat | git fast-import
 323 </pre>
 324
 325   </li>
 326
 327   <li>If you want to get rid of unnecessary tag fixup branches, then
 328     run the <tt>contrib/git-move-refs.py</tt> script from within the
 329     git repository.</li>
 330
 331 </ol>
 332
 333 <p>Feedback would be much appreciated, including reports of success
 334   using cvs2git.  Please send comments, bug reports, and patches to
 335   the <a
 336   href="http://cvs2svn.tigris.org/servlets/ProjectMailingListList">cvs2svn
 337   mailing lists</a>.</p>
 338
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