[PATCH] MinGW: fix diff --no-index /dev/null ...

When launching "diff --no-index" with a parameter "/dev/null", the MSys
bash converts the "/dev/null" to a "nul", which usually makes sense.  But
diff --no-index got confused and tried to access a _file_ called "nul".

While at it, the comment in t4012, expressed as ":# <text>" was turned
into ": <text>" so that MSys' path name mangling does not kick in.

With this patch, t4012 passes in msysGit.

Signed-off-by: Johannes Schindelin <redacted>
---
 diff-no-index.c        |    4 ++++
 t/t4012-diff-binary.sh |    2 +-
 2 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/diff-no-index.c b/diff-no-index.c
index 0a14268..598687b 100644
--- a/diff-no-index.c
+++ b/diff-no-index.c

@@ -38,6 +38,10 @@ static int get_mode(const char *path, int *mode)
 
 	if (!path || !strcmp(path, "/dev/null"))
 		*mode = 0;
+#ifdef _WIN32
+	else if (!strcasecmp(path, "nul"))
+		*mode = 0;
+#endif
 	else if (!strcmp(path, "-"))
 		*mode = create_ce_mode(0666);
 	else if (lstat(path, &st))

diff --git a/t/t4012-diff-binary.sh b/t/t4012-diff-binary.sh
index 3cf5b5c..f64aa48 100755
--- a/t/t4012-diff-binary.sh
+++ b/t/t4012-diff-binary.sh

@@ -87,7 +87,7 @@ nul_to_q() {
 
 test_expect_success 'diff --no-index with binary creation' '
 	echo Q | q_to_nul >binary &&
-	(:# hide error code from diff, which just indicates differences
+	(: hide error code from diff, which just indicates differences
 	 git diff --binary --no-index /dev/null binary >current ||
 	 true
 	) &&

-- 
1.6.2.327.g0fa6c

On Samstag, 7. März 2009, Johannes Schindelin wrote:

IMO this #ifdef is a reasonable compromise. Trying to move this into 
git-compat-util.h or mingw.h somehow would only obfuscate the code.

Tested-by: Johannes Sixt <redacted>

-- Hannes

Johannes Schindelin [off-list ref] writes:

I had a brief "Huh? -- doesn't this call for an is_dev_null() helper"
moment, but I think you are right that diff-no-index.c is the right place
to special case it.

Should this go to 'maint'?

Hi,

On Sat, 7 Mar 2009, Junio C Hamano wrote:

Johannes Schindelin [off-list ref] writes:

quoted

diff --git a/diff-no-index.c b/diff-no-index.c
index 0a14268..598687b 100644
--- a/diff-no-index.c
+++ b/diff-no-index.c

@@ -38,6 +38,10 @@ static int get_mode(const char *path, int *mode)
 
 	if (!path || !strcmp(path, "/dev/null"))
 		*mode = 0;
+#ifdef _WIN32
+	else if (!strcasecmp(path, "nul"))
+		*mode = 0;
+#endif
 	else if (!strcmp(path, "-"))
 		*mode = create_ce_mode(0666);
 	else if (lstat(path, &st))

I had a brief "Huh? -- doesn't this call for an is_dev_null() helper"
moment, but I think you are right that diff-no-index.c is the right place
to special case it.

You're right, it needs to be explained in the commit message.  So how 
about this:

-- snip --
Unlike other places where a string is compared to /dev/null, in this case 
do not parse a diff, but rather command line parameters that have 
possibly been transformed from /dev/null to nul, so that the file can be 
opened.
-- snap --

If you like it, may I ask you to amend the message?

Should this go to 'maint'?

Technically, yes, as it is a fix.

However, it might not be necessary, as literally all Windows work on Git 
happens in git/mingw.git, git/mingw/j6t.git and git/mingw/4msysgit.git.

Your call.

Thanks,
Dscho

On Samstag, 7. März 2009, Junio C Hamano wrote:

Should this go to 'maint'?

I don't think that's necessary. It fixes only that someone literally writes on 
the Windows command line

   git diff --no-index nul foo.c

when on Unix one would have written

   git diff --no-index /dev/null foo.c

In practice, only the test suite does this ;)

-- Hannes