Correct mispellings of ".gitmodule" to ".gitmodules"

There are a small number of misspellings, ".gitmodule", scattered
throughout the code base, correct them ... no apparent functional
changes.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/api-submodule-config.txt

@@ -4,7 +4,7 @@ submodule config cache API
 The submodule config cache API allows to read submodule
 configurations/information from specified revisions. Internally
 information is lazily read into a cache that is used to avoid
-unnecessary parsing of the same .gitmodule files. Lookups can be done by
+unnecessary parsing of the same .gitmodules files. Lookups can be done by
 submodule path or name.
 Usage

contrib/subtree/git-subtree.txt

@@ -28,7 +28,7 @@ as a subdirectory of your application.
 Subtrees are not to be confused with submodules, which are meant for
 the same task. Unlike submodules, subtrees do not need any special
-constructions (like .gitmodule files or gitlinks) be present in
+constructions (like .gitmodules files or gitlinks) be present in
 your repository, and do not force end-users of your
 repository to do anything special or to understand how subtrees
 work. A subtree is just a subdirectory that can be

submodule-config.c

@@ -9,7 +9,7 @@
 /*
  * submodule cache lookup structure
  * There is one shared set of 'struct submodule' entries which can be
- * looked up by their sha1 blob id of the .gitmodule file and either
+ * looked up by their sha1 blob id of the .gitmodules file and either
  * using path or name as key.
  * for_path stores submodule entries with path as key
  * for_name stores submodule entries with name as key
@@ -91,7 +91,7 @@ static void submodule_cache_clear(struct submodule_cache *cache)
 	/*
 	 * We iterate over the name hash here to be symmetric with the
 	 * allocation of struct submodule entries. Each is allocated by
-	 * their .gitmodule blob sha1 and submodule name.
+	 * their .gitmodules blob sha1 and submodule name.
 	 */
 	hashmap_iter_init(&cache->for_name, &iter);
 	while ((entry = hashmap_iter_next(&iter)))

t/t5526-fetch-submodules.sh

@@ -485,7 +485,7 @@ test_expect_success "don't fetch submodule when newly recorded commits are alrea
 	)
 '
-test_expect_success "'fetch.recurseSubmodules=on-demand' works also without .gitmodule entry" '
+test_expect_success "'fetch.recurseSubmodules=on-demand' works also without .gitmodules entry" '
 	(
 		cd downstream &&
 		git fetch --recurse-submodules