3.9 Issues with Version Control Systems

If a project stores its source files in a version control system (VCS), such as CVS, Subversion, or Git, one needs to decide which files to commit.

In principle, all files created by gnulib-tool, except gnulib-cache.m4, can be treated like generated source files, like for example a parser.c file generated from parser.y. Alternatively, they can be considered source files and updated manually.

Here are the three different approaches in common use. Each has its place, and you should use whichever best suits your particular project and development methods.

1. In projects which commit all source files, whether generated or not, into their VCS, the gnulib-tool generated files should all be committed. In this case, you should pass the option ‘--no-vc-files’ to gnulib-tool, which avoids alteration of VCS-related files such as .gitignore.

   Gnulib also contains files generated by make (and removed by make clean), using information determined by configure. For a Gnulib source file of the form lib/foo.in.h, the corresponding lib/foo.h is such a make-generated file. These should not be checked into the VCS, but instead added to .gitignore or equivalent.

2. In projects which customarily omit from their VCS all files that are generated from other source files, none of these files and directories are added into the VCS. As described in Modified imports, there are two ways to keep track of options and module names that are passed to gnulib-tool. The command for restoring the omitted files depends on it:
   • If they are stored in a file other than gnulib-cache.m4, such as autogen.sh, bootstrap, bootstrap.conf, or similar, the restoration command is the entire gnulib-tool ... --import ... invocation with all options and module names.
   • If the project relies on gnulib-tool’s memory of the last used options and module names, then the file gnulib-cache.m4 in the M4 macros directory must be added to the VCS, and the restoration command is:

     $ gnulib-tool --update
     

     The ‘--update’ option operates much like the ‘--add-import’ option, but it does not offer the possibility to change the way Gnulib is used. Also it does not report in the ChangeLogs the files that it had to add because they were missing.

   Gnulib includes the file build-aux/bootstrap to aid a developer in using this setup. Furthermore, in projects that use git for version control, it is possible to use a git submodule containing the precise commit of the gnulib repository, so that each developer running bootstrap will get the same version of all gnulib-provided files. The location of the submodule can be chosen to fit the package’s needs; here’s how to initially create the submodule in the directory .gnulib:

   $ dir=.gnulib
   $ git submodule add -- git://git.sv.gnu.org/gnulib.git $dir
   $ git config alias.syncsub "submodule foreach git pull origin master"
   

   Thereafter, bootstrap can run this command to update the submodule to the recorded checkout level:

   git submodule update --init $dir
   

   and a developer can use this sequence to update to a newer version of gnulib:

   $ git syncsub
   $ git add $dir
   $ ./bootstrap
   

3. Some projects take a “middle road”: they do commit Gnulib source files as in the first approach, but they do not commit other derived files, such as a Makefile.in generated by Automake. This increases the size and complexity of the repository, but can help occasional contributors by not requiring them to have a full Gnulib checkout to do a build, and all developers by ensuring that all developers are working with the same version of Gnulib in the repository. It also supports multiple Gnulib instances within a project. It remains important not to commit the make-generated files, as described above.