[PATCH 13/21] rev-parse: add '--absolute-git-dir' option

["SZEDER Gábor" <szeder@ira.uka.de>]

Some scripts can benefit from not having to deal with the possibility
of relative paths to the repository, but the output of 'git rev-parse
--git-dir' can be a relative path.  Case in point: supporting 'git -C
<path>' in our Bash completion script turned out to be considerably
more difficult, error prone and required more subshells and git
processes when we had to cope with a relative path to the .git
directory.

Help these use cases and teach 'git rev-parse' a new
'--absolute-git-dir' option which always outputs a canonicalized
absolute path to the .git directory, regardless of whether the path is
discovered automatically or is specified via $GIT_DIR or 'git
--git-dir=<path>'.

Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
---
 Documentation/git-rev-parse.txt |  4 ++++
 builtin/rev-parse.c             | 29 +++++++++++++++++++++--------
 t/t1500-rev-parse.sh            | 17 ++++++++++-------
 3 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index b6c6326cdc7b..fb06e3118570 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -216,6 +216,10 @@ If `$GIT_DIR` is not defined and the current directory
 is not detected to lie in a Git repository or work tree
 print a message to stderr and exit with nonzero status.
 
+--absolute-git-dir::
+	Like `--git-dir`, but its output is always the canonicalized
+	absolute path.
+
 --git-common-dir::
 	Show `$GIT_COMMON_DIR` if defined, else `$GIT_DIR`.
 
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index cf8487b3b95f..90a4dd6032c0 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -744,17 +744,30 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				putchar('\n');
 				continue;
 			}
-			if (!strcmp(arg, "--git-dir")) {
+			if (!strcmp(arg, "--git-dir") ||
+			    !strcmp(arg, "--absolute-git-dir")) {
 				const char *gitdir = getenv(GIT_DIR_ENVIRONMENT);
 				char *cwd;
 				int len;
-				if (gitdir) {
-					puts(gitdir);
-					continue;
-				}
-				if (!prefix) {
-					puts(".git");
-					continue;
+				if (arg[2] == 'g') {	/* --git-dir */
+					if (gitdir) {
+						puts(gitdir);
+						continue;
+					}
+					if (!prefix) {
+						puts(".git");
+						continue;
+					}
+				} else {		/* --absolute-git-dir */
+					if (!gitdir && !prefix)
+						gitdir = ".git";
+					if (gitdir) {
+						char absolute_path[PATH_MAX];
+						if (!realpath(gitdir, absolute_path))
+							die_errno(_("unable to get absolute path"));
+						puts(absolute_path);
+						continue;
+					}
 				}
 				cwd = xgetcwd();
 				len = strlen(cwd);
diff --git a/t/t1500-rev-parse.sh b/t/t1500-rev-parse.sh
index 48ee07779d64..617fcd821309 100755
--- a/t/t1500-rev-parse.sh
+++ b/t/t1500-rev-parse.sh
@@ -31,23 +31,26 @@ test_rev_parse() {
 	"test '$1' = \"\$(git rev-parse --git-dir)\""
 	shift
 	[ $# -eq 0 ] && return
+
+	test_expect_success "$name: absolute-git-dir" \
+	"verbose test '$1' = \"\$(git rev-parse --absolute-git-dir)\""
 }
 
-# label is-bare is-inside-git is-inside-work prefix git-dir
+# label is-bare is-inside-git is-inside-work prefix git-dir absolute-git-dir
 
 ROOT=$(pwd)
 
-test_rev_parse toplevel false false true '' .git
+test_rev_parse toplevel false false true '' .git "$ROOT/.git"
 
 cd .git || exit 1
-test_rev_parse .git/ false true false '' .
+test_rev_parse .git/ false true false '' . "$ROOT/.git"
 cd objects || exit 1
-test_rev_parse .git/objects/ false true false '' "$ROOT/.git"
+test_rev_parse .git/objects/ false true false '' "$ROOT/.git" "$ROOT/.git"
 cd ../.. || exit 1
 
 mkdir -p sub/dir || exit 1
 cd sub/dir || exit 1
-test_rev_parse subdirectory false false true sub/dir/ "$ROOT/.git"
+test_rev_parse subdirectory false false true sub/dir/ "$ROOT/.git" "$ROOT/.git"
 cd ../.. || exit 1
 
 git config core.bare true
@@ -63,7 +66,7 @@ GIT_CONFIG="$(pwd)"/../.git/config
 export GIT_DIR GIT_CONFIG
 
 git config core.bare false
-test_rev_parse 'GIT_DIR=../.git, core.bare = false' false false true ''
+test_rev_parse 'GIT_DIR=../.git, core.bare = false' false false true '' "../.git" "$ROOT/.git"
 
 git config core.bare true
 test_rev_parse 'GIT_DIR=../.git, core.bare = true' true false false ''
@@ -76,7 +79,7 @@ GIT_DIR=../repo.git
 GIT_CONFIG="$(pwd)"/../repo.git/config
 
 git config core.bare false
-test_rev_parse 'GIT_DIR=../repo.git, core.bare = false' false false true ''
+test_rev_parse 'GIT_DIR=../repo.git, core.bare = false' false false true '' "../repo.git" "$ROOT/repo.git"
 
 git config core.bare true
 test_rev_parse 'GIT_DIR=../repo.git, core.bare = true' true false false ''
-- 
2.7.2.410.g92cb358