Re: [PATCH/RFC v1 1/1] cygwin: Allow pushing to UNC paths

tboegi@web.de writes:

From: Torsten Bögershausen <redacted>

cygwin can use an UNC path like //server/share/repo
$ cd //server/share/dir
$ mkdir test
$ cd test
$ git init --bare

However, when we try to push from a local Git repository to this repo,
there are 2 problems:
- Git converts the leading "//" into a single "/".
- The remote repo is not accepted because setup.c calls
  access(getenv(DB_ENVIRONMENT), X_OK)
  and this call fails. In other words, checking the executable bit
  of a directory mounted on a SAMBA share is not reliable (and not needed).

As cygwin handles an UNC path so well, Git can support them better.
- Introduce cygwin_offset_1st_component() which keeps the leading "//",
  similar to what Git for Windows does.
- Move CYGWIN out of the POSIX in the tests for path normalization in t0060.
- Use cygwin_access() with a relaxed test for the executable bit on
  a directory pointed out by an UNC path.

Thanks.

The offset-1st-component thing looks like a right thing to do.

I think the reason why you marked this as RFC is because you found
the "access" bit a bit iffy?  If so, I share the feeling.  If it
were called only from the codepath in setup.c::is_git_directory(),
it may be OK, but I suspect that there are other places that do care
about access() for other reasons in the codebase, and I am not sure
if it is safe to change the behaviour of access() like this.

Stepping back a bit.

The implementation of is_git_directory() wants to ensure that the
top level of the object database (i.e.  $GIT_OBJECT_DIRECTORY or
$GIT_DIR/objects) and the reference store (i.e. $GIT_DIR/refs) can
be "executed".  But what it really wants to see is that it is a
directory we can search.  If we had a regular file that is executable,
it would happily say "Yes!", even though that is clearly bogus and
not a Git repository.

So perhaps we would want a bit higher-level abstraction API
implemented as:

	int is_searchable_directory(const char *path)
	{
		struct stat st;

	        return (!stat(path, &st) && S_ISDIR(st.st_mode));
	}

on Cygwin (as SMB share may not give you correct access(2)), and

	int is_searchable_directory(const char *path)
	{
		struct stat st;

	        return (!stat(path, &st) && 
			S_ISDIR(st.st_mode) &&
			!access(path, X_OK));
	}

elsewhere, or something like that, and use that in the
implementation of is_git_directory()?

I dunno.  I see compat/mingw.c discards X_OK the same way you did,
so perhaps your version is a right solution at least in the shorter
term anyway.  

Regardless, I think that we would want to make sure that the thing
is a directory where is_git_directory() uses access(2).  But that
could be an orthogonal issue.