[PATCH] git: extend --no-lazy-fetch to work across subprocesses

[Junio C Hamano <gitster@pobox.com>]

Modeling after how the `--no-replace-objects` option is made usable
across subprocess spawning (e.g., cURL based remote helpers are
spawned as a separate process while running "git fetch"), allow the
`--no-lazy-fetch` option to be passed across process boundary.

Do not model how the value of GIT_NO_REPLACE_OBJECTS environment
variable is ignored, though.  Just use the usual git_env_bool() to
allow "export GIT_NO_LAZY_FETCH=0" and "unset GIT_NO_LAZY_FETCH"
to be equivalents.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

 * And this comes on top of the original one plus the documentation
   update for GIT_NO_REPLACE_OBJECTS.

 Documentation/git.txt    | 2 ++
 environment.c            | 4 ++++
 environment.h            | 1 +
 git.c                    | 3 +++
 t/t0410-partial-clone.sh | 9 +++++++++
 5 files changed, 19 insertions(+)

diff --git a/Documentation/git.txt b/Documentation/git.txt
index 2f1cb3ef4e..be2829003d 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -183,6 +183,8 @@ If you just want to run git as if it was started in `<path>` then use
 	Do not fetch missing objects from the promisor remote on
 	demand.  Useful together with `git cat-file -e <object>` to
 	see if the object is locally available.
+	This is equivalent to setting the `GIT_NO_LAZY_FETCH`
+	environment variable to `1`.
 
 --literal-pathspecs::
 	Treat pathspecs literally (i.e. no globbing, no pathspec magic).
diff --git a/environment.c b/environment.c
index 9e37bf58c0..afad78a3f8 100644
--- a/environment.c
+++ b/environment.c
@@ -136,6 +136,7 @@ const char * const local_repo_env[] = {
 	GRAFT_ENVIRONMENT,
 	INDEX_ENVIRONMENT,
 	NO_REPLACE_OBJECTS_ENVIRONMENT,
+	NO_LAZY_FETCH_ENVIRONMENT,
 	GIT_REPLACE_REF_BASE_ENVIRONMENT,
 	GIT_PREFIX_ENVIRONMENT,
 	GIT_SHALLOW_FILE_ENVIRONMENT,
@@ -207,6 +208,9 @@ void setup_git_env(const char *git_dir)
 	shallow_file = getenv(GIT_SHALLOW_FILE_ENVIRONMENT);
 	if (shallow_file)
 		set_alternate_shallow_file(the_repository, shallow_file, 0);
+
+	if (git_env_bool(NO_LAZY_FETCH_ENVIRONMENT, 0))
+		fetch_if_missing = 0;
 }
 
 int is_bare_repository(void)
diff --git a/environment.h b/environment.h
index e5351c9dd9..74b3124f55 100644
--- a/environment.h
+++ b/environment.h
@@ -35,6 +35,7 @@ const char *getenv_safe(struct strvec *argv, const char *name);
 #define EXEC_PATH_ENVIRONMENT "GIT_EXEC_PATH"
 #define CEILING_DIRECTORIES_ENVIRONMENT "GIT_CEILING_DIRECTORIES"
 #define NO_REPLACE_OBJECTS_ENVIRONMENT "GIT_NO_REPLACE_OBJECTS"
+#define NO_LAZY_FETCH_ENVIRONMENT "GIT_NO_LAZY_FETCH"
 #define GIT_REPLACE_REF_BASE_ENVIRONMENT "GIT_REPLACE_REF_BASE"
 #define GITATTRIBUTES_FILE ".gitattributes"
 #define INFOATTRIBUTES_FILE "info/attributes"
diff --git a/git.c b/git.c
index 28e8bf7497..d11d4dc77b 100644
--- a/git.c
+++ b/git.c
@@ -189,6 +189,9 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 				*envchanged = 1;
 		} else if (!strcmp(cmd, "--no-lazy-fetch")) {
 			fetch_if_missing = 0;
+			setenv(NO_LAZY_FETCH_ENVIRONMENT, "1", 1);
+			if (envchanged)
+				*envchanged = 1;
 		} else if (!strcmp(cmd, "--no-replace-objects")) {
 			disable_replace_refs();
 			setenv(NO_REPLACE_OBJECTS_ENVIRONMENT, "1", 1);
diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index 5b7bee888d..59629cea1f 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -665,6 +665,15 @@ test_expect_success 'lazy-fetch when accessing object not in the_repository' '
 	git -C partial.git rev-list --objects --missing=print HEAD >out &&
 	grep "[?]$FILE_HASH" out &&
 
+	# The no-lazy-fetch mechanism prevents Git from fetching
+	test_must_fail env GIT_NO_LAZY_FETCH=1 \
+		git -C partial.git cat-file -e "$FILE_HASH" &&
+	test_must_fail git --no-lazy-fetch -C partial.git cat-file -e "$FILE_HASH" &&
+
+	# Sanity check that the file is still missing
+	git -C partial.git rev-list --objects --missing=print HEAD >out &&
+	grep "[?]$FILE_HASH" out &&
+
 	git -C full cat-file -s "$FILE_HASH" >expect &&
 	test-tool partial-clone object-info partial.git "$FILE_HASH" >actual &&
 	test_cmp expect actual &&
-- 
2.44.0-rc1-17-g3e0d3cd5c7