Re: ./bootstrap --gnulib-srcdir and GNULIB_REVISION

[Bruno Haible]

Hi Simon,

> Bug #2: ./bootstrap writes to the path indicated by --gnulib-srcdir with
> the 'git checkout' command, and leaves the --gnulib-srcdir path at that
> commit after ./bootstrap is finished.  This happens to work in my
> example since I pointed it to a writable work tree, but I think altering
> that path is unexpected and not documented.  Imagine pointing this to a
> system-wide gnulib .git store like --gnulib-srcdir=/usr/share/src/gnulib
> or similar read-only place.  Or imagine multiple ./bootstrap running at
> the same time for different projects, both pointing to the same gnulib
> .git work tree.  I think the path indicated by --gnulib-srcdir should be
> read-only.

If --gnulib-srcdir is given and GNULIB_REVISION is set in bootstrap.conf:

* The current behaviour (now independent of submodule or not) is that
  - Without --no-git, the GNULIB_REVISION is checked out in $GNULIB_SRCDIR.
    If this directory has local modifications, git reports an error, and
    'bootstrap' fails. If it does not have local modifications, the
    $GNULIB_SRCDIR is left in that modified state.
  - With --no-git, the contents of $GNULIB_SRCDIR is left unmodified.

  So, the user has the possibility to force the behaviour they desire.

* But I agree that it would be useful to change

  "If the environment variable GNULIB_SRCDIR is set, then sources are
   fetched from that local directory.  If it is a git repository and the
   configuration variable GNULIB_REVISION is set in bootstrap.conf, then
   that revision is checked out."

  to

  "If the environment variable GNULIB_SRCDIR is set, then sources are
   fetched from that local directory.  If the configuration variable
   GNULIB_REVISION is set in bootstrap.conf, it is ignored."

  for 3 reasons:

    - As a simple-to-remember rule, $GNULIB_SRCDIR would always be left
      unmodified.

    - The purpose of GNULIB_REVISION is to simulate a submodule without
      actually having a git submodule. Only very few packages use this:
      GNU make, man-db, libpipeline, binfmt-support. Probably they wanted
      to avoid submodules because of the extra learning curve associated
      with git submodules.
      The submodule is only considered in the case that GNULIB_SRCDIR
      is not set. Therefore, it would be consistent to consider GNULIB_REVISION
      also only when GNULIB_SRCDIR is not set.

    - The recipe for using a modified gnulib
        ./bootstrap --no-git --gnulib-srcdir=...
      would be simplified to
        ./bootstrap --gnulib-srcdir=...

  And what would a user do who was using GNULIB_SRCDIR and _wants_ the
  GNULIB_REVISION to be respected? They would set GNULIB_REFDIR instead of
  GNULIB_SRCDIR. (This is precisely the point of GNULIB_REFDIR!)

Bruno