read-tree: add "--super-prefix" option, eliminate global

The "--super-prefix" option to "git" was initially added in [1] for
use with "ls-files"[2], and shortly thereafter "submodule--helper"[3]
and "grep"[4]. It wasn't until [5] that "read-tree" made use of it.

At the time [5] made sense, but since then we've made "ls-files"
recurse in-process in [6], "grep" in [7], and finally
"submodule--helper" in the preceding commits.

Let's also remove it from "read-tree", which allows us to remove the
option to "git" itself.

We can do this because the only remaining user of it is the submodule
API, which will now invoke "read-tree" with its new "--super-prefix"
option. It will only do so when the "submodule_move_head()" function
is called.

That "submodule_move_head()" function was then only invoked by
"read-tree" itself, but now rather than setting an environment
variable to pass "--super-prefix" between cmd_read_tree() we:

- Set a new "super_prefix" in "struct unpack_trees_options". The
  "super_prefixed()" function in "unpack-trees.c" added in [5] will now
  use this, rather than get_super_prefix() looking up the environment
  variable we set earlier in the same process.

- Add the same field to the "struct checkout", which is only needed to
  ferry the "super_prefix" in the "struct unpack_trees_options" all the
  way down to the "entry.c" callers of "submodule_move_head()".

  Those calls which used the super prefix all originated in
  "cmd_read_tree()". The only other caller is the "unlink_entry()"
  caller in "builtin/checkout.c", which now passes a "NULL".

1. 74866d75793 (git: make super-prefix option, 2016-10-07)
2. e77aa336f11 (ls-files: optionally recurse into submodules, 2016-10-07)
3. 89c86265576 (submodule helper: support super prefix, 2016-12-08)
4. 0281e487fd9 (grep: optionally recurse into submodules, 2016-12-16)
5. 3d415425c7b (unpack-trees: support super-prefix option, 2017-01-17)
6. 188dce131fa (ls-files: use repository object, 2017-06-22)
7. f9ee2fcdfa0 (grep: recurse in-process using 'struct repository', 2017-08-02)

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 0 insertions, 13 deletions

diff --git a/environment.c b/environment.c
index 18d042b467..1ee3686fd8 100644
--- a/environment.c
+++ b/environment.c
@@ -102,8 +102,6 @@ char *git_work_tree_cfg;
 
 static char *git_namespace;
 
-static char *super_prefix;
-
 /*
  * Repository-local GIT_* environment variables; see cache.h for details.
  */
@@ -121,7 +119,6 @@ const char * const local_repo_env[] = {
 	NO_REPLACE_OBJECTS_ENVIRONMENT,
 	GIT_REPLACE_REF_BASE_ENVIRONMENT,
 	GIT_PREFIX_ENVIRONMENT,
-	GIT_SUPER_PREFIX_ENVIRONMENT,
 	GIT_SHALLOW_FILE_ENVIRONMENT,
 	GIT_COMMON_DIR_ENVIRONMENT,
 	NULL
@@ -234,16 +231,6 @@ const char *strip_namespace(const char *namespaced_ref)
 	return NULL;
 }
 
-const char *get_super_prefix(void)
-{
-	static int initialized;
-	if (!initialized) {
-		super_prefix = xstrdup_or_null(getenv(GIT_SUPER_PREFIX_ENVIRONMENT));
-		initialized = 1;
-	}
-	return super_prefix;
-}
-
 static int git_work_tree_initialized;
 
 /*