[PATCH 1/4 v4] submodules: make submodule-prefix option

[Brandon Williams <bmwill@google.com>]

Add a submodule-prefix environment variable
'GIT_INTERNAL_SUBMODULE_PREFIX' which can be used by commands which have
--recurse-submodule options to give context to submodules about how they
were invoked.  This option is only allowed for builtins which have
submodule support.

Signed-off-by: Brandon Williams <bmwill@google.com>
---
 Documentation/git.txt |  5 +++++
 cache.h               |  1 +
 environment.c         |  1 +
 git.c                 | 19 +++++++++++++++++++
 4 files changed, 26 insertions(+)

diff --git a/Documentation/git.txt b/Documentation/git.txt
index 7913fc2..d29967a 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -13,6 +13,7 @@ SYNOPSIS
     [--exec-path[=<path>]] [--html-path] [--man-path] [--info-path]
     [-p|--paginate|--no-pager] [--no-replace-objects] [--bare]
     [--git-dir=<path>] [--work-tree=<path>] [--namespace=<name>]
+    [--submodule-prefix=<path>]
     <command> [<args>]
 
 DESCRIPTION
@@ -601,6 +602,10 @@ foo.bar= ...`) sets `foo.bar` to the empty string.
 	details.  Equivalent to setting the `GIT_NAMESPACE` environment
 	variable.
 
+--submodule-prefix=<path>::
+	Set a prefix which gives submodules context about the superproject that
+	invoked it.  Only allowed for commands which support submodules.
+
 --bare::
 	Treat the repository as a bare repository.  If GIT_DIR
 	environment is not set, it is set to the current working
diff --git a/cache.h b/cache.h
index 3556326..ae88a35 100644
--- a/cache.h
+++ b/cache.h
@@ -408,6 +408,7 @@ static inline enum object_type object_type(unsigned int mode)
 #define GIT_NAMESPACE_ENVIRONMENT "GIT_NAMESPACE"
 #define GIT_WORK_TREE_ENVIRONMENT "GIT_WORK_TREE"
 #define GIT_PREFIX_ENVIRONMENT "GIT_PREFIX"
+#define GIT_SUBMODULE_PREFIX_ENVIRONMENT "GIT_INTERNAL_SUBMODULE_PREFIX"
 #define DEFAULT_GIT_DIR_ENVIRONMENT ".git"
 #define DB_ENVIRONMENT "GIT_OBJECT_DIRECTORY"
 #define INDEX_ENVIRONMENT "GIT_INDEX_FILE"
diff --git a/environment.c b/environment.c
index ca72464..7380815 100644
--- a/environment.c
+++ b/environment.c
@@ -120,6 +120,7 @@ const char * const local_repo_env[] = {
 	NO_REPLACE_OBJECTS_ENVIRONMENT,
 	GIT_REPLACE_REF_BASE_ENVIRONMENT,
 	GIT_PREFIX_ENVIRONMENT,
+	GIT_SUBMODULE_PREFIX_ENVIRONMENT,
 	GIT_SHALLOW_FILE_ENVIRONMENT,
 	GIT_COMMON_DIR_ENVIRONMENT,
 	NULL
diff --git a/git.c b/git.c
index 1c61151..b2b096a 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, "--submodule-prefix")) {
+			if (*argc < 2) {
+				fprintf(stderr, "No prefix given for --submodule-prefix.\n" );
+				usage(git_usage_string);
+			}
+			setenv(GIT_SUBMODULE_PREFIX_ENVIRONMENT, (*argv)[1], 1);
+			if (envchanged)
+				*envchanged = 1;
+			(*argv)++;
+			(*argc)--;
+		} else if (skip_prefix(cmd, "--submodule-prefix=", &cmd)) {
+			setenv(GIT_SUBMODULE_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_SUBMODULES	(1<<4)
 
 struct cmd_struct {
 	const char *cmd;
@@ -344,6 +359,10 @@ static int run_builtin(struct cmd_struct *p, int argc, const char **argv)
 	}
 	commit_pager_choice();
 
+	if (!help && (getenv(GIT_SUBMODULE_PREFIX_ENVIRONMENT) &&
+		      !(p->option & SUPPORT_SUBMODULES)))
+		die("%s doesn't support submodules", p->cmd);
+
 	if (!help && p->option & NEED_WORK_TREE)
 		setup_work_tree();
 
-- 
2.8.0.rc3.226.g39d4020