Merge branch 'js/expand-runtime-prefix'

Pathname expansion (like "~username/") learned a way to specify a
location relative to Git installation (e.g. its $sharedir which is
$(prefix)/share), with "%(prefix)".

* js/expand-runtime-prefix:
  expand_user_path: allow in-flight topics to keep using the old name
  interpolate_path(): allow specifying paths relative to the runtime prefix
  Use a better name for the function interpolating paths
  expand_user_path(): clarify the role of the `real_home` parameter
  expand_user_path(): remove stale part of the comment
  tests: exercise the RUNTIME_PREFIX feature

10 files changed, 64 insertions, 15 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index bf82766a6a..0c0e6b859f 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -298,6 +298,15 @@ pathname::
 	tilde expansion happens to such a string: `~/`
 	is expanded to the value of `$HOME`, and `~user/` to the
 	specified user's home directory.
++
+If a path starts with `%(prefix)/`, the remainder is interpreted as a
+path relative to Git's "runtime prefix", i.e. relative to the location
+where Git itself was installed. For example, `%(prefix)/bin/` refers to
+the directory in which the Git executable itself lives. If Git was
+compiled without runtime prefix support, the compiled-in prefix will be
+subsituted instead. In the unlikely event that a literal path needs to
+be specified that should _not_ be expanded, it needs to be prefixed by
+`./`, like so: `./%(prefix)/bin`.
 
 
 Variables
diff --git a/Makefile b/Makefile
index 9573190f1d..3452aaab14 100644
--- a/Makefile
+++ b/Makefile
@@ -2849,6 +2849,11 @@ endif
 ifdef GIT_TEST_PERL_FATAL_WARNINGS
 	@echo GIT_TEST_PERL_FATAL_WARNINGS=\''$(subst ','\'',$(subst ','\'',$(GIT_TEST_PERL_FATAL_WARNINGS)))'\' >>$@+
 endif
+ifdef RUNTIME_PREFIX
+	@echo RUNTIME_PREFIX=\'true\' >>$@+
+else
+	@echo RUNTIME_PREFIX=\'false\' >>$@+
+endif
 	@if cmp $@+ $@ >/dev/null 2>&1; then $(RM) $@+; else mv $@+ $@; fi
 
 ### Detect Python interpreter path changes
diff --git a/builtin/credential-cache.c b/builtin/credential-cache.c
index 76a6ba3722..e8a7415747 100644
--- a/builtin/credential-cache.c
+++ b/builtin/credential-cache.c
@@ -90,7 +90,7 @@ static char *get_socket_path(void)
 {
 	struct stat sb;
 	char *old_dir, *socket;
-	old_dir = expand_user_path("~/.git-credential-cache", 0);
+	old_dir = interpolate_path("~/.git-credential-cache", 0);
 	if (old_dir && !stat(old_dir, &sb) && S_ISDIR(sb.st_mode))
 		socket = xstrfmt("%s/socket", old_dir);
 	else
diff --git a/builtin/credential-store.c b/builtin/credential-store.c
index ae3c1ba75f..62a4f3c265 100644
--- a/builtin/credential-store.c
+++ b/builtin/credential-store.c
@@ -173,7 +173,7 @@ int cmd_credential_store(int argc, const char **argv, const char *prefix)
 	if (file) {
 		string_list_append(&fns, file);
 	} else {
-		if ((file = expand_user_path("~/.git-credentials", 0)))
+		if ((file = interpolate_path("~/.git-credentials", 0)))
 			string_list_append_nodup(&fns, file);
 		file = xdg_config_home("credentials");
 		if (file)
diff --git a/builtin/gc.c b/builtin/gc.c
index f05d2f0a1a..6ce5ca4512 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -1542,7 +1542,7 @@ static char *launchctl_service_filename(const char *name)
 	struct strbuf filename = STRBUF_INIT;
 	strbuf_addf(&filename, "~/Library/LaunchAgents/%s.plist", name);
 
-	expanded = expand_user_path(filename.buf, 1);
+	expanded = interpolate_path(filename.buf, 1);
 	if (!expanded)
 		die(_("failed to expand path '%s'"), filename.buf);
 
diff --git a/cache.h b/cache.h
index bd4869beee..d23de69368 100644
--- a/cache.h
+++ b/cache.h
@@ -1255,7 +1255,9 @@ typedef int create_file_fn(const char *path, void *cb);
 int raceproof_create_file(const char *path, create_file_fn fn, void *cb);
 
 int mkdir_in_gitdir(const char *path);
-char *expand_user_path(const char *path, int real_home);
+char *interpolate_path(const char *path, int real_home);
+/* NEEDSWORK: remove this synonym once in-flight topics have migrated */
+#define expand_user_path interpolate_path
 const char *enter_repo(const char *path, int strict);
 static inline int is_absolute_path(const char *path)
 {
diff --git a/config.c b/config.c
index f33abeab85..cb4a8058bf 100644
--- a/config.c
+++ b/config.c
@@ -137,7 +137,7 @@ static int handle_path_include(const char *path, struct config_include_data *inc
 	if (!path)
 		return config_error_nonbool("include.path");
 
-	expanded = expand_user_path(path, 0);
+	expanded = interpolate_path(path, 0);
 	if (!expanded)
 		return error(_("could not expand include path '%s'"), path);
 	path = expanded;
@@ -185,7 +185,7 @@ static int prepare_include_condition_pattern(struct strbuf *pat)
 	char *expanded;
 	int prefix = 0;
 
-	expanded = expand_user_path(pat->buf, 1);
+	expanded = interpolate_path(pat->buf, 1);
 	if (expanded) {
 		strbuf_reset(pat);
 		strbuf_addstr(pat, expanded);
@@ -1270,7 +1270,7 @@ int git_config_pathname(const char **dest, const char *var, const char *value)
 {
 	if (!value)
 		return config_error_nonbool(var);
-	*dest = expand_user_path(value, 0);
+	*dest = interpolate_path(value, 0);
 	if (!*dest)
 		die(_("failed to expand user dir in: '%s'"), value);
 	return 0;
@@ -1845,7 +1845,7 @@ void git_global_config(char **user_out, char **xdg_out)
 	char *xdg_config = NULL;
 
 	if (!user_config) {
-		user_config = expand_user_path("~/.gitconfig", 0);
+		user_config = interpolate_path("~/.gitconfig", 0);
 		xdg_config = xdg_config_home("config");
 	}
 
diff --git a/path.c b/path.c
index 7bccd830e9..0bc788ea40 100644
--- a/path.c
+++ b/path.c
@@ -12,6 +12,7 @@
 #include "packfile.h"
 #include "object-store.h"
 #include "lockfile.h"
+#include "exec-cmd.h"
 
 static int get_st_mode_bits(const char *path, int *mode)
 {
@@ -719,19 +720,25 @@ static struct passwd *getpw_str(const char *username, size_t len)
 }
 
 /*
- * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
- * then it is a newly allocated string. Returns NULL on getpw failure or
- * if path is NULL.
+ * Return a string with ~ and ~user expanded via getpw*. Returns NULL on getpw
+ * failure or if path is NULL.
  *
- * If real_home is true, strbuf_realpath($HOME) is used in the expansion.
+ * If real_home is true, strbuf_realpath($HOME) is used in the `~/` expansion.
+ *
+ * If the path starts with `%(prefix)/`, the remainder is interpreted as
+ * relative to where Git is installed, and expanded to the absolute path.
  */
-char *expand_user_path(const char *path, int real_home)
+char *interpolate_path(const char *path, int real_home)
 {
 	struct strbuf user_path = STRBUF_INIT;
 	const char *to_copy = path;
 
 	if (path == NULL)
 		goto return_null;
+
+	if (skip_prefix(path, "%(prefix)/", &path))
+		return system_path(path);
+
 	if (path[0] == '~') {
 		const char *first_slash = strchrnul(path, '/');
 		const char *username = path + 1;
@@ -812,7 +819,7 @@ const char *enter_repo(const char *path, int strict)
 		strbuf_add(&validated_path, path, len);
 
 		if (used_path.buf[0] == '~') {
-			char *newpath = expand_user_path(used_path.buf, 0);
+			char *newpath = interpolate_path(used_path.buf, 0);
 			if (!newpath)
 				return NULL;
 			strbuf_attach(&used_path, newpath, strlen(newpath),
diff --git a/sequencer.c b/sequencer.c
index 7f07cd00f3..7483ee3a76 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1241,7 +1241,7 @@ N_("Your name and email address were configured automatically based\n"
 
 static const char *implicit_ident_advice(void)
 {
-	char *user_config = expand_user_path("~/.gitconfig", 0);
+	char *user_config = interpolate_path("~/.gitconfig", 0);
 	char *xdg_config = xdg_config_home("config");
 	int config_exists = file_exists(user_config) || file_exists(xdg_config);
 
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index de4960783f..34d1061f32 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -525,4 +525,30 @@ test_expect_success MINGW 'is_valid_path() on Windows' '
 		"PRN./abc"
 '
 
+test_lazy_prereq RUNTIME_PREFIX '
+	test true = "$RUNTIME_PREFIX"
+'
+
+test_lazy_prereq CAN_EXEC_IN_PWD '
+	cp "$GIT_EXEC_PATH"/git$X ./ &&
+	./git rev-parse
+'
+
+test_expect_success RUNTIME_PREFIX,CAN_EXEC_IN_PWD 'RUNTIME_PREFIX works' '
+	mkdir -p pretend/bin pretend/libexec/git-core &&
+	echo "echo HERE" | write_script pretend/libexec/git-core/git-here &&
+	cp "$GIT_EXEC_PATH"/git$X pretend/bin/ &&
+	GIT_EXEC_PATH= ./pretend/bin/git here >actual &&
+	echo HERE >expect &&
+	test_cmp expect actual'
+
+test_expect_success RUNTIME_PREFIX,CAN_EXEC_IN_PWD '%(prefix)/ works' '
+	mkdir -p pretend/bin &&
+	cp "$GIT_EXEC_PATH"/git$X pretend/bin/ &&
+	git config yes.path "%(prefix)/yes" &&
+	GIT_EXEC_PATH= ./pretend/bin/git config --path yes.path >actual &&
+	echo "$(pwd)/pretend/yes" >expect &&
+	test_cmp expect actual
+'
+
 test_done