[PATCH v2] Make git_dir a path relative to work_tree in setup_work_tree()

Once we find the absolute paths for git_dir and work_tree, we can make
git_dir a relative path since we know pwd will be work_tree. This should
save the kernel some time traversing the path to work_tree all the time
if git_dir is inside work_tree.

Signed-off-by: Daniel Barkalow <redacted>
---
Not only was work_tree potentially NULL, it was also already a copied 
canonical path. So this simpler patch should be better.

 cache.h |    1 +
 path.c  |   17 +++++++++++++++++
 setup.c |    3 ++-
 3 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/cache.h b/cache.h
index eab1a17..3465c94 100644
--- a/cache.h
+++ b/cache.h

@@ -524,6 +524,7 @@ static inline int is_absolute_path(const char *path)
 	return path[0] == '/';
 }
 const char *make_absolute_path(const char *path);
+const char *make_relative_path(const char *abs, const char *base);
 
 /* Read and unpack a sha1 file into memory, write memory to a sha1 file */
 extern int sha1_object_info(const unsigned char *, unsigned long *);

diff --git a/path.c b/path.c
index b7c24a2..790d8d4 100644
--- a/path.c
+++ b/path.c

@@ -294,6 +294,23 @@ int adjust_shared_perm(const char *path)
 /* We allow "recursive" symbolic links. Only within reason, though. */
 #define MAXDEPTH 5
 
+const char *make_relative_path(const char *abs, const char *base)
+{
+	static char buf[PATH_MAX + 1];
+	int baselen;
+	if (!base)
+		return abs;
+	baselen = strlen(base);
+	if (prefixcmp(abs, base))
+		return abs;
+	if (abs[baselen] == '/')
+		baselen++;
+	else if (base[baselen - 1] != '/')
+		return abs;
+	strcpy(buf, abs + baselen);
+	return buf;
+}
+
 const char *make_absolute_path(const char *path)
 {
 	static char bufs[2][PATH_MAX + 1], *buf = bufs[0], *next_buf = bufs[1];

diff --git a/setup.c b/setup.c
index d630e37..1643ee4 100644
--- a/setup.c
+++ b/setup.c

@@ -292,7 +292,8 @@ void setup_work_tree(void)
 	work_tree = get_git_work_tree();
 	git_dir = get_git_dir();
 	if (!is_absolute_path(git_dir))
-		set_git_dir(make_absolute_path(git_dir));
+		set_git_dir(make_relative_path(make_absolute_path(git_dir),
+					       work_tree));
 	if (!work_tree || chdir(work_tree))
 		die("This operation must be run in a work tree");
 	initialized = 1;

-- 
1.5.4.5

Hi,

On Wed, 18 Jun 2008, Daniel Barkalow wrote:

I suspect it needs "work_tree &&" here.

-		set_git_dir(make_absolute_path(git_dir));
+		set_git_dir(make_relative_path(make_absolute_path(git_dir),
+					       work_tree));
 	if (!work_tree || chdir(work_tree))
 		die("This operation must be run in a work tree");
 	initialized = 1;

All in all I am pretty surprised how easy it was.  I tried yesterday, for 
half an hour, to come up with something sensible, and failed.

Thanks,
Dscho

On Thu, 19 Jun 2008, Johannes Schindelin wrote:

Hi,

On Wed, 18 Jun 2008, Daniel Barkalow wrote:

quoted

diff --git a/setup.c b/setup.c
index d630e37..1643ee4 100644
--- a/setup.c
+++ b/setup.c

@@ -292,7 +292,8 @@ void setup_work_tree(void)
 	work_tree = get_git_work_tree();
 	git_dir = get_git_dir();
 	if (!is_absolute_path(git_dir))

I suspect it needs "work_tree &&" here.

I'm not clear on the semantics of !get_git_work_tree(); is a non-absolute 
path for git_dir right then?

quoted

-		set_git_dir(make_absolute_path(git_dir));
+		set_git_dir(make_relative_path(make_absolute_path(git_dir),
+					       work_tree));
 	if (!work_tree || chdir(work_tree))
 		die("This operation must be run in a work tree");
 	initialized = 1;

All in all I am pretty surprised how easy it was.  I tried yesterday, for 
half an hour, to come up with something sensible, and failed.

I was sure you'd come up with just this solution, because you'd just 
recently explained that make_absolute_path() means you can find when one 
path is in another path with a simple string compare. And, since we know 
what pwd is going to be...

	-Daniel
*This .sig left intentionally blank*

Hi,

On Thu, 19 Jun 2008, Daniel Barkalow wrote:

On Thu, 19 Jun 2008, Johannes Schindelin wrote:

quoted

On Wed, 18 Jun 2008, Daniel Barkalow wrote:

quoted

diff --git a/setup.c b/setup.c
index d630e37..1643ee4 100644
--- a/setup.c
+++ b/setup.c

@@ -292,7 +292,8 @@ void setup_work_tree(void)
 	work_tree = get_git_work_tree();
 	git_dir = get_git_dir();
 	if (!is_absolute_path(git_dir))

I suspect it needs "work_tree &&" here.

I'm not clear on the semantics of !get_git_work_tree(); is a non-absolute 
path for git_dir right then?

My reading was: if there is no work_tree, then a relative git_dir is just 
fine, since we are quite unlikely to jump around in the file system.

And your implementation of make_relative_path() is nice enough to a 
(work_tree ==) base == NULL, but would return the absolute path in that 
case.

Haven't had time to test anything, though.

Ciao,
Dscho