[PATCH v2 0/2] meson: prefer '/bin/sh' over PATH lookup

Hi,

at GitLab, we recently got a couple of bug reports about Git not being able to find its shell anymore. The root cause is that with Meson we have started to look up the shell via PATH, which may exist on the build host, but not on the target host. We have worked around this issue with a cross file:

    $ cat >cross.ini <<-EOF
    [binaries]
    sh = '/bin/sh'
    EOF
    $ meson setup build --cross-file=./cross.ini

But this made me remember the report from Peter [1] that Debian also faced this issue. So I decided to address the issue in Meson directly by preferring `/bin/sh` over a PATH-based lookup.

Changes in v2:
  - Simplify how we generate the summary.
  - Add a comment to explain ordering of the program path.
  - Link to v1: https://lore.kernel.org/r/20250424-pks-meson-posix-shell-v1-0-45e06ee4b6ad@pks.im

Thanks!

Patrick

[1]: <20250209133027.64a865aa@gmx.net>

---
Patrick Steinhardt (2):
      meson: report detected runtime executable paths
      meson: prefer POSIX-specified shell path

 meson.build | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

Range-diff versus v1:

1:  cdb4db30677 ! 1:  b606f3ffe2e meson: report detected runtime executable paths
    @@ meson.build: summary({
      }, section: 'Backends')
     +
     +summary({
    -+  'perl': target_perl.found() ? target_perl.full_path() : 'none',
    -+  'python': target_python.found() ? target_python.full_path() : 'none',
    -+  'shell': target_shell.full_path(),
    ++  'perl': target_perl,
    ++  'python': target_python,
    ++  'shell': target_shell,
     +}, section: 'Runtime executable paths')
2:  d439c859fbb ! 2:  3804c32b879 meson: prefer POSIX-specified shell path
    @@ meson.build: sed = find_program('sed', dirs: program_path, native: true)
      tar = find_program('tar', dirs: program_path, native: true)
      
     -target_shell = find_program('sh', dirs: program_path, native: false)
    ++# Detect the target shell that is used by Git at runtime. Note that we prefer
    ++# '/bin/sh' over a PATH-based lookup given that '/bin/sh' is the location
    ++# specified by POSIX. This lookup can be overridden via `program_path`.
     +target_shell = find_program('sh', dirs: program_path + [ '/bin' ], native: false)
      
      # Sanity-check that programs required for the build exist.

--- base-commit: a2955b34f48265d240ab8c7deb0a929ec2d65fd0 change-id: 20250424-pks-meson-posix-shell-4969161025c5