Re: [PATCH/RFC v1 1/1] cygwin: Allow pushing to UNC paths
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Jun 28, 2017, 17:40 UTC
- Message-ID
- <xmqqefu4vwn0.fsf@gitster.mtv.corp.google.com>
- In-Reply-To
- <20170628162958.519-1-tboegi@web.de>
tboegi@web.de writes:
Show 22 quoted lines
> From: Torsten Bögershausen <tboegi@web.de> > > 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.
Show 98 quoted lines
> Signed-off-by: Torsten Bögershausen <tboegi@web.de>
> ---
> compat/cygwin.c | 29 +++++++++++++++++++++++++++++
> compat/cygwin.h | 7 +++++++
> config.mak.uname | 1 +
> git-compat-util.h | 3 +++
> t/t0060-path-utils.sh | 2 ++
> 5 files changed, 42 insertions(+)
> create mode 100644 compat/cygwin.c
> create mode 100644 compat/cygwin.h
>
> diff --git a/compat/cygwin.c b/compat/cygwin.c
> new file mode 100644
> index 0000000..d98e877
> --- /dev/null
> +++ b/compat/cygwin.c
> @@ -0,0 +1,29 @@
> +#include "../git-compat-util.h"
> +#include "../cache.h"
> +
> +int cygwin_offset_1st_component(const char *path)
> +{
> + const char *pos = path;
> + /* unc paths */
> + if (is_dir_sep(pos[0]) && is_dir_sep(pos[1])) {
> + /* skip server name */
> + pos = strchr(pos + 2, '/');
> + if (!pos)
> + return 0; /* Error: malformed unc path */
> +
> + do {
> + pos++;
> + } while (*pos && pos[0] != '/');
> + }
> + return pos + is_dir_sep(*pos) - path;
> +}
> +
> +#undef access
> +int cygwin_access(const char *filename, int mode)
> +{
> + /* the execute bit does not work on SAMBA drives */
> + if (filename[0] == '/' && filename[1] == '/' )
> + return access(filename, mode & ~X_OK);
> + else
> + return access(filename, mode);
> +}
> diff --git a/compat/cygwin.h b/compat/cygwin.h
> new file mode 100644
> index 0000000..efa12ad
> --- /dev/null
> +++ b/compat/cygwin.h
> @@ -0,0 +1,7 @@
> +int cygwin_access(const char *filename, int mode);
> +#undef access
> +#define access cygwin_access
> +
> +
> +int cygwin_offset_1st_component(const char *path);
> +#define offset_1st_component cygwin_offset_1st_component
> diff --git a/config.mak.uname b/config.mak.uname
> index adfb90b..551e465 100644
> --- a/config.mak.uname
> +++ b/config.mak.uname
> @@ -184,6 +184,7 @@ ifeq ($(uname_O),Cygwin)
> UNRELIABLE_FSTAT = UnfortunatelyYes
> SPARSE_FLAGS = -isystem /usr/include/w32api -Wno-one-bit-signed-bitfield
> OBJECT_CREATION_USES_RENAMES = UnfortunatelyNeedsTo
> + COMPAT_OBJS += compat/cygwin.o
> endif
> ifeq ($(uname_S),FreeBSD)
> NEEDS_LIBICONV = YesPlease
> diff --git a/git-compat-util.h b/git-compat-util.h
> index 047172d..db9c22d 100644
> --- a/git-compat-util.h
> +++ b/git-compat-util.h
> @@ -189,6 +189,9 @@
> #include <sys/sysctl.h>
> #endif
>
> +#if defined(__CYGWIN__)
> +#include "compat/cygwin.h"
> +#endif
> #if defined(__MINGW32__)
> /* pull in Windows compatibility stuff */
> #include "compat/mingw.h"
> diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
> index 444b5a4..7ea2bb5 100755
> --- a/t/t0060-path-utils.sh
> +++ b/t/t0060-path-utils.sh
> @@ -70,6 +70,8 @@ ancestor() {
> case $(uname -s) in
> *MINGW*)
> ;;
> +*CYGWIN*)
> + ;;
> *)
> test_set_prereq POSIX
> ;;