Re: [PATCH v5 1/2] setup: distingush ENOENT from other stat errors

Junio C Hamano [off-list ref] writes:

Tian Yuchen [off-list ref] writes:

quoted

Currently, 'read_gitfile_gently()' treats all 'stat()' failures as
generic errors. This prevents distinguishing between a missing file and
real errors like permission denied (fatal).

The above plan makes sense---you would split stat() error into two
different classes, start returning ERR_STAT_NOENT in addition to
ERR_STAT_FAILED, have the caller act on the new ERR_STAT_NOENT and
adjust the way it acts on ERR_STAT_FAILED, and if possible add tests
to make sure we react to failures from stat in an appropriate way
(but how? --- it is where my "if possible" comes from).  So I would
expect that the other patch would be to split ERR_NOT_A_FILE and add
ERR_IS_A_DIR, have the caller act on the new ERR_IS_A_DIR and adjust
the way it acts on ERR_NOT_A_FILE.

I forgot to say one thing.

When changing the external interface for these service functions
like read_gitfile_gently() and read_gitfile_error_die(), we need to
make sure the change will not break _other_ callers of them, outside
our main focus area.  The latter, for example, has a caller in
submodule.c and we need to make sure that the existing code is
reacting to the updated definition of what ERR_STAT_FAILED and
ERR_NOT_A_FILE mean (and if not, adjust it).  read_gitfile_gently()
is used more widely outside setup.c and we need to audit these
callers, too.