git: make super-prefix option

Add a super-prefix environment variable 'GIT_INTERNAL_SUPER_PREFIX'
which can be used to specify a path from above a repository down to its
root.  When such a super-prefix is specified, the paths reported by Git
are prefixed with it to make them relative to that directory "above".
The paths given by the user on the command line
(e.g. "git subcmd --output-file=path/to/a/file" and pathspecs) are taken
relative to the directory "above" to match.

The immediate use of this option is by commands which have a
--recurse-submodule option in order to give context to submodules about
how they were invoked.  This option is currently only allowed for
builtins which support a super-prefix.

Signed-off-by: Brandon Williams <bmwill@google.com>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/git.c b/git.c
index 1c6115175..469a83f2b 100644
--- a/git.c
+++ b/git.c
@@ -164,6 +164,20 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 			setenv(GIT_WORK_TREE_ENVIRONMENT, cmd, 1);
 			if (envchanged)
 				*envchanged = 1;
+		} else if (!strcmp(cmd, "--super-prefix")) {
+			if (*argc < 2) {
+				fprintf(stderr, "No prefix given for --super-prefix.\n" );
+				usage(git_usage_string);
+			}
+			setenv(GIT_SUPER_PREFIX_ENVIRONMENT, (*argv)[1], 1);
+			if (envchanged)
+				*envchanged = 1;
+			(*argv)++;
+			(*argc)--;
+		} else if (skip_prefix(cmd, "--super-prefix=", &cmd)) {
+			setenv(GIT_SUPER_PREFIX_ENVIRONMENT, cmd, 1);
+			if (envchanged)
+				*envchanged = 1;
 		} else if (!strcmp(cmd, "--bare")) {
 			char *cwd = xgetcwd();
 			is_bare_repository_cfg = 1;
@@ -310,6 +324,7 @@ static int handle_alias(int *argcp, const char ***argv)
  * RUN_SETUP for reading from the configuration file.
  */
 #define NEED_WORK_TREE		(1<<3)
+#define SUPPORT_SUPER_PREFIX	(1<<4)
 
 struct cmd_struct {
 	const char *cmd;
@@ -344,6 +359,13 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 	}
 	commit_pager_choice();
 
+	if (!help && get_super_prefix()) {
+		if (!(p->option & SUPPORT_SUPER_PREFIX))
+			die("%s doesn't support --super-prefix", p->cmd);
+		if (prefix)
+			die("can't use --super-prefix from a subdirectory");
+	}
+
 	if (!help && p->option & NEED_WORK_TREE)
 		setup_work_tree();
 
@@ -558,6 +580,9 @@ static void execv_dashed_external(const char **argv)
 	const char *tmp;
 	int status;
 
+	if (get_super_prefix())
+		die("%s doesn't support --super-prefix", argv[0]);
+
 	if (use_pager == -1)
 		use_pager = check_pager_config(argv[0]);
 	commit_pager_choice();