rev-parse: add option for absolute or relative path formatting

git rev-parse has several options which print various paths.  Some of
these paths are printed relative to the current working directory, and
some are absolute.

Normally, this is not a problem, but there are times when one wants
paths entirely in one format or another.  This can be done trivially if
the paths are canonical, but canonicalizing paths is not possible on
some shell scripting environments which lack realpath(1) and also in Go,
which lacks functions that properly canonicalize paths on Windows.

To help out the scripter, let's provide an option which turns most of
the paths printed by git rev-parse to be either relative to the current
working directory or absolute and canonical.  Document which options are
affected and which are not so that users are not confused.

This approach is cleaner and tidier than providing duplicates of
existing options which are either relative or absolute.

Note that if the user needs both forms, it is possible to pass an
additional option in the middle of the command line which changes the
behavior of subsequent operations.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 194 insertions, 43 deletions

diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index 5013daa6ef..6b8ca085aa 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -212,6 +212,18 @@ Options for Files
 	Only the names of the variables are listed, not their value,
 	even if they are set.
 
+--path-format=(absolute|relative)::
+	Controls the behavior of certain other options. If specified as absolute, the
+	paths printed by those options will be absolute and canonical. If specified as
+	relative, the paths will be relative to the current working directory if that
+	is possible.  The default is option specific.
++
+This option may be specified multiple times and affects only the arguments that
+follow it on the command line, either to the end of the command line or the next
+instance of this option.
+
+The following options are modified by `--path-format`:
+
 --git-dir::
 	Show `$GIT_DIR` if defined. Otherwise show the path to
 	the .git directory. The path shown, when relative, is
@@ -221,27 +233,9 @@ If `$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`.
 
---is-inside-git-dir::
-	When the current working directory is below the repository
-	directory print "true", otherwise "false".
-
---is-inside-work-tree::
-	When the current working directory is inside the work tree of the
-	repository print "true", otherwise "false".
-
---is-bare-repository::
-	When the repository is bare print "true", otherwise "false".
-
---is-shallow-repository::
-	When the repository is shallow print "true", otherwise "false".
-
 --resolve-git-dir <path>::
 	Check if <path> is a valid repository or a gitfile that
 	points at a valid repository, and print the location of the
@@ -255,19 +249,9 @@ print a message to stderr and exit with nonzero status.
 	$GIT_OBJECT_DIRECTORY is set to /foo/bar then "git rev-parse
 	--git-path objects/abc" returns /foo/bar/abc.
 
---show-cdup::
-	When the command is invoked from a subdirectory, show the
-	path of the top-level directory relative to the current
-	directory (typically a sequence of "../", or an empty string).
-
---show-prefix::
-	When the command is invoked from a subdirectory, show the
-	path of the current directory relative to the top-level
-	directory.
-
 --show-toplevel::
-	Show the absolute path of the top-level directory of the working
-	tree. If there is no working tree, report an error.
+	Show the (by default, absolute) path of the top-level directory
+	of the working tree. If there is no working tree, report an error.
 
 --show-superproject-working-tree::
 	Show the absolute path of the root of the superproject's
@@ -279,6 +263,36 @@ print a message to stderr and exit with nonzero status.
 	Show the path to the shared index file in split index mode, or
 	empty if not in split-index mode.
 
+The following options are unaffected by `--path-format`:
+
+--absolute-git-dir::
+	Like `--git-dir`, but its output is always the canonicalized
+	absolute path.
+
+--is-inside-git-dir::
+	When the current working directory is below the repository
+	directory print "true", otherwise "false".
+
+--is-inside-work-tree::
+	When the current working directory is inside the work tree of the
+	repository print "true", otherwise "false".
+
+--is-bare-repository::
+	When the repository is bare print "true", otherwise "false".
+
+--is-shallow-repository::
+	When the repository is shallow print "true", otherwise "false".
+
+--show-cdup::
+	When the command is invoked from a subdirectory, show the
+	path of the top-level directory relative to the current
+	directory (typically a sequence of "../", or an empty string).
+
+--show-prefix::
+	When the command is invoked from a subdirectory, show the
+	path of the current directory relative to the top-level
+	directory.
+
 --show-object-format[=(storage|input|output)]::
 	Show the object format (hash algorithm) used for the repository
 	for storage inside the `.git` directory, input, or output. For
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 69ba7326cf..85bad9052e 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -583,6 +583,75 @@ static void handle_ref_opt(const char *pattern, const char *prefix)
 	clear_ref_exclusion(&ref_excludes);
 }
 
+enum format_type {
+	/* We would like a relative path. */
+	FORMAT_RELATIVE,
+	/* We would like a canonical absolute path. */
+	FORMAT_CANONICAL,
+	/* We would like the default behavior. */
+	FORMAT_DEFAULT,
+};
+
+enum default_type {
+	/* Our default is a relative path. */
+	DEFAULT_RELATIVE,
+	/* Our default is a relative path if there's a shared root. */
+	DEFAULT_RELATIVE_IF_SHARED,
+	/* Our default is a canonical absolute path. */
+	DEFAULT_CANONICAL,
+	/* Our default is not to modify the item. */
+	DEFAULT_UNMODIFIED,
+};
+
+static void print_path(const char *path, const char *prefix, enum format_type format, enum default_type def)
+{
+	char *cwd = NULL;
+	/*
+	 * We don't ever produce a relative path if prefix is NULL, so set the
+	 * prefix to the current directory so that we can produce a relative
+	 * path whenever possible.  If we're using RELATIVE_IF_SHARED mode, then
+	 * we want an absolute path unless the two share a common prefix, so don't
+	 * set it in that case, since doing so causes a relative path to always
+	 * be produced if possible.
+	 */
+	if (!prefix && (format != FORMAT_DEFAULT || def != DEFAULT_RELATIVE_IF_SHARED))
+		prefix = cwd = xgetcwd();
+	if (format == FORMAT_DEFAULT && def == DEFAULT_UNMODIFIED) {
+		puts(path);
+	} else if (format == FORMAT_RELATIVE ||
+		  (format == FORMAT_DEFAULT && def == DEFAULT_RELATIVE)) {
+		/*
+		 * In order for relative_path to work as expected, we need to
+		 * make sure that both paths are absolute paths.  If we don't,
+		 * we can end up with an unexpected absolute path that the user
+		 * didn't want.
+		 */
+		struct strbuf buf = STRBUF_INIT, realbuf = STRBUF_INIT, prefixbuf = STRBUF_INIT;
+		if (!is_absolute_path(path)) {
+			strbuf_realpath_forgiving(&realbuf, path,  1);
+			path = realbuf.buf;
+		}
+		if (!is_absolute_path(prefix)) {
+			strbuf_realpath_forgiving(&prefixbuf, prefix, 1);
+			prefix = prefixbuf.buf;
+		}
+		puts(relative_path(path, prefix, &buf));
+		strbuf_release(&buf);
+		strbuf_release(&realbuf);
+		strbuf_release(&prefixbuf);
+	} else if (format == FORMAT_DEFAULT && def == DEFAULT_RELATIVE_IF_SHARED) {
+		struct strbuf buf = STRBUF_INIT;
+		puts(relative_path(path, prefix, &buf));
+		strbuf_release(&buf);
+	} else {
+		struct strbuf buf = STRBUF_INIT;
+		strbuf_realpath_forgiving(&buf, path, 1);
+		puts(buf.buf);
+		strbuf_release(&buf);
+	}
+	free(cwd);
+}
+
 int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 {
 	int i, as_is = 0, verify = 0, quiet = 0, revs_count = 0, type = 0;
@@ -596,6 +665,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 	struct strbuf buf = STRBUF_INIT;
 	const int hexsz = the_hash_algo->hexsz;
 	int seen_end_of_options = 0;
+	enum format_type format = FORMAT_DEFAULT;
 
 	if (argc > 1 && !strcmp("--parseopt", argv[1]))
 		return cmd_parseopt(argc - 1, argv + 1, prefix);
@@ -668,8 +738,9 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				if (!argv[i + 1])
 					die("--git-path requires an argument");
 				strbuf_reset(&buf);
-				puts(relative_path(git_path("%s", argv[i + 1]),
-						   prefix, &buf));
+				print_path(git_path("%s", argv[i + 1]), prefix,
+						format,
+						DEFAULT_RELATIVE_IF_SHARED);
 				i++;
 				continue;
 			}
@@ -687,6 +758,16 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 					show(arg);
 				continue;
 			}
+			if (opt_with_value(arg, "--path-format", &arg)) {
+				if (!strcmp(arg, "absolute")) {
+					format = FORMAT_CANONICAL;
+				} else if (!strcmp(arg, "relative")) {
+					format = FORMAT_RELATIVE;
+				} else {
+					die("unknown argument to --path-format: %s", arg);
+				}
+				continue;
+			}
 			if (!strcmp(arg, "--default")) {
 				def = argv[++i];
 				if (!def)
@@ -807,7 +888,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 			if (!strcmp(arg, "--show-toplevel")) {
 				const char *work_tree = get_git_work_tree();
 				if (work_tree)
-					puts(work_tree);
+					print_path(work_tree, prefix, format, DEFAULT_UNMODIFIED);
 				else
 					die("this operation must be run in a work tree");
 				continue;
@@ -815,7 +896,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 			if (!strcmp(arg, "--show-superproject-working-tree")) {
 				struct strbuf superproject = STRBUF_INIT;
 				if (get_superproject_working_tree(&superproject))
-					puts(superproject.buf);
+					print_path(superproject.buf, prefix, format, DEFAULT_UNMODIFIED);
 				strbuf_release(&superproject);
 				continue;
 			}
@@ -850,16 +931,18 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				const char *gitdir = getenv(GIT_DIR_ENVIRONMENT);
 				char *cwd;
 				int len;
+				enum format_type wanted = format;
 				if (arg[2] == 'g') {	/* --git-dir */
 					if (gitdir) {
-						puts(gitdir);
+						print_path(gitdir, prefix, format, DEFAULT_UNMODIFIED);
 						continue;
 					}
 					if (!prefix) {
-						puts(".git");
+						print_path(".git", prefix, format, DEFAULT_UNMODIFIED);
 						continue;
 					}
 				} else {		/* --absolute-git-dir */
+					wanted = FORMAT_CANONICAL;
 					if (!gitdir && !prefix)
 						gitdir = ".git";
 					if (gitdir) {
@@ -872,14 +955,14 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				}
 				cwd = xgetcwd();
 				len = strlen(cwd);
-				printf("%s%s.git\n", cwd, len && cwd[len-1] != '/' ? "/" : "");
+				strbuf_reset(&buf);
+				strbuf_addf(&buf, "%s%s.git", cwd, len && cwd[len-1] != '/' ? "/" : "");
 				free(cwd);
+				print_path(buf.buf, prefix, wanted, DEFAULT_CANONICAL);
 				continue;
 			}
 			if (!strcmp(arg, "--git-common-dir")) {
-				strbuf_reset(&buf);
-				puts(relative_path(get_git_common_dir(),
-						   prefix, &buf));
+				print_path(get_git_common_dir(), prefix, format, DEFAULT_RELATIVE_IF_SHARED);
 				continue;
 			}
 			if (!strcmp(arg, "--is-inside-git-dir")) {
@@ -909,8 +992,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				if (the_index.split_index) {
 					const struct object_id *oid = &the_index.split_index->base_oid;
 					const char *path = git_path("sharedindex.%s", oid_to_hex(oid));
-					strbuf_reset(&buf);
-					puts(relative_path(path, prefix, &buf));
+					print_path(path, prefix, format, DEFAULT_RELATIVE);
 				}
 				continue;
 			}
diff --git a/t/t1500-rev-parse.sh b/t/t1500-rev-parse.sh
index 408b97d5af..51d7d40ec1 100755
--- a/t/t1500-rev-parse.sh
+++ b/t/t1500-rev-parse.sh
@@ -3,6 +3,16 @@
 test_description='test git rev-parse'
 . ./test-lib.sh
 
+test_one () {
+	dir="$1" &&
+	expect="$2" &&
+	shift &&
+	shift &&
+	echo "$expect" >expect &&
+	git -C "$dir" rev-parse "$@" >actual &&
+	test_cmp expect actual
+}
+
 # usage: [options] label is-bare is-inside-git is-inside-work prefix git-dir absolute-git-dir
 test_rev_parse () {
 	d=
@@ -60,7 +70,13 @@ ROOT=$(pwd)
 
 test_expect_success 'setup' '
 	mkdir -p sub/dir work &&
-	cp -R .git repo.git
+	cp -R .git repo.git &&
+	git checkout -B main &&
+	test_commit abc &&
+	git checkout -b side &&
+	test_commit def &&
+	git checkout main &&
+	git worktree add worktree side
 '
 
 test_rev_parse toplevel false false true '' .git "$ROOT/.git"
@@ -88,6 +104,45 @@ test_rev_parse -C work -g ../repo.git -b t 'GIT_DIR=../repo.git, core.bare = tru
 
 test_rev_parse -C work -g ../repo.git -b u 'GIT_DIR=../repo.git, core.bare undefined' false false true ''
 
+test_expect_success 'rev-parse --path-format=absolute' '
+	test_one "." "$ROOT/.git" --path-format=absolute --git-dir &&
+	test_one "." "$ROOT/.git" --path-format=absolute --git-common-dir &&
+	test_one "sub/dir" "$ROOT/.git" --path-format=absolute --git-dir &&
+	test_one "sub/dir" "$ROOT/.git" --path-format=absolute --git-common-dir &&
+	test_one "worktree" "$ROOT/.git/worktrees/worktree" --path-format=absolute --git-dir &&
+	test_one "worktree" "$ROOT/.git" --path-format=absolute --git-common-dir &&
+	test_one "." "$ROOT" --path-format=absolute --show-toplevel &&
+	test_one "." "$ROOT/.git/objects" --path-format=absolute --git-path objects &&
+	test_one "." "$ROOT/.git/objects/foo/bar/baz" --path-format=absolute --git-path objects/foo/bar/baz
+'
+
+test_expect_success 'rev-parse --path-format=relative' '
+	test_one "." ".git" --path-format=relative --git-dir &&
+	test_one "." ".git" --path-format=relative --git-common-dir &&
+	test_one "sub/dir" "../../.git" --path-format=relative --git-dir &&
+	test_one "sub/dir" "../../.git" --path-format=relative --git-common-dir &&
+	test_one "worktree" "../.git/worktrees/worktree" --path-format=relative --git-dir &&
+	test_one "worktree" "../.git" --path-format=relative --git-common-dir &&
+	test_one "." "./" --path-format=relative --show-toplevel &&
+	test_one "." ".git/objects" --path-format=relative --git-path objects &&
+	test_one "." ".git/objects/foo/bar/baz" --path-format=relative --git-path objects/foo/bar/baz
+'
+
+test_expect_success '--path-format=relative does not affect --absolute-git-dir' '
+	git rev-parse --path-format=relative --absolute-git-dir >actual &&
+	echo "$ROOT/.git" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '--path-format can change in the middle of the command line' '
+	git rev-parse --path-format=absolute --git-dir --path-format=relative --git-path objects/foo/bar >actual &&
+	cat >expect <<-EOF &&
+	$ROOT/.git
+	.git/objects/foo/bar
+	EOF
+	test_cmp expect actual
+'
+
 test_expect_success 'git-common-dir from worktree root' '
 	echo .git >expect &&
 	git rev-parse --git-common-dir >actual &&