[PATCH] rev-parse --git-path: fix output when running in a subdirectory

[Johannes Schindelin <johannes.schindelin@gmx.de>]

In addition to making git_path() aware of certain file names that need
to be handled differently e.g. when running in worktrees, the commit
557bd833bb (git_path(): be aware of file relocation in $GIT_DIR,
2014-11-30) also snuck in a new option for `git rev-parse`:
`--git-path`.

On the face of it, there is no obvious bug in that commit's diff: it
faithfully calls git_path() on the argument and prints it out, i.e. `git
rev-parse --git-path <filename>` has the same precise behavior as
calling `git_path("<filename>")` in C.

The problem lies deeper, much deeper. In hindsight (which is always
unfair), implementing the .git/ directory discovery in
`setup_git_directory()` by changing the working directory may have
allowed us to avoid passing around a struct that contains information
about the current repository, but it bought us many, many problems.

In this case, when being called in a subdirectory, `git rev-parse`
changes the working directory to the top-level directory before calling
`git_path()`. In the new working directory, the result is correct. But
in the working directory of the calling script, it is incorrect.

Example: when calling `git rev-parse --git-path HEAD` in, say, the
Documentation/ subdirectory of Git's own source code, the string
`.git/HEAD` is printed.

Side note: that bug is hidden when running in a subdirectory of a
worktree that was added by the `git worktree` command: in that case, the
(correct) absolute path of the `HEAD` file is printed.

In the interest of time, this patch does not go the "correct" route to
introduce a struct with repository information (and removing global
state in the process), instead this patch chooses to detect when the
command was called in a subdirectory and forces the result to be an
absolute path.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
Published-As: https://github.com/dscho/git/releases/tag/git-path-in-subdir-v1
Fetch-It-Via: git fetch https://github.com/dscho/git git-path-in-subdir-v1

 builtin/rev-parse.c   | 6 +++++-
 t/t0060-path-utils.sh | 2 ++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index ff13e59e1d..f9d5762bf2 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -597,9 +597,13 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 		}
 
 		if (!strcmp(arg, "--git-path")) {
+			const char *path;
 			if (!argv[i + 1])
 				die("--git-path requires an argument");
-			puts(git_path("%s", argv[i + 1]));
+			path = git_path("%s", argv[i + 1]);
+			if (prefix && !is_absolute_path(path))
+				path = real_path(path);
+			puts(path);
 			i++;
 			continue;
 		}
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 444b5a4df8..790584fcc5 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -271,6 +271,8 @@ relative_path "<null>"		"<empty>"	./
 relative_path "<null>"		"<null>"	./
 relative_path "<null>"		/foo/a/b	./
 
+test_git_path "mkdir sub && cd sub && test_when_finished cd .. &&" \
+	foo "$(pwd)/.git/foo"
 test_git_path A=B                info/grafts .git/info/grafts
 test_git_path GIT_GRAFT_FILE=foo info/grafts foo
 test_git_path GIT_GRAFT_FILE=foo info/////grafts foo

base-commit: 6e3a7b3398559305c7a239a42e447c21a8f39ff8
-- 
2.11.1.windows.1