add -i: default to the built-in implementation

In 9a5315edfd (Merge branch 'js/patch-mode-in-others-in-c',
2020-02-05), Git acquired a built-in implementation of `git add`'s
interactive mode that could be turned on via the config option
`add.interactive.useBuiltin`.

The first official Git version to support this knob was v2.26.0.

In 2df2d81ddd (add -i: use the built-in version when
feature.experimental is set, 2020-09-08), this built-in implementation
was also enabled via `feature.experimental`. The first version with this
change was v2.29.0.

More than a year (and very few bug reports) later, it is time to declare
the built-in implementation mature and to turn it on by default.

We specifically leave the `add.interactive.useBuiltin` configuration in
place, to give users an "escape hatch" in the unexpected case should
they encounter a previously undetected bug in that implementation.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/add.txt

@@ -7,6 +7,6 @@ add.ignore-errors (deprecated)::
 	variables.
 
 add.interactive.useBuiltin::
-	[EXPERIMENTAL] Set to `true` to use the experimental built-in
-	implementation of the interactive version of linkgit:git-add[1]
-	instead of the Perl script version. Is `false` by default.
+	Set to `false` to fall back to the original Perl implementation of
+	the interactive version of linkgit:git-add[1] instead of the built-in
+	version. Is `true` by default.

builtin/add.c

@@ -237,17 +237,12 @@ int run_add_interactive(const char *revision, const char *patch_mode,
 	int use_builtin_add_i =
 		git_env_bool("GIT_TEST_ADD_I_USE_BUILTIN", -1);
 
-	if (use_builtin_add_i < 0) {
-		int experimental;
-		if (!git_config_get_bool("add.interactive.usebuiltin",
-					 &use_builtin_add_i))
-			; /* ok */
-		else if (!git_config_get_bool("feature.experimental", &experimental) &&
-			 experimental)
-			use_builtin_add_i = 1;
-	}
+	if (use_builtin_add_i < 0 &&
+	    git_config_get_bool("add.interactive.usebuiltin",
+				&use_builtin_add_i))
+		use_builtin_add_i = 1;
 
-	if (use_builtin_add_i == 1) {
+	if (use_builtin_add_i != 0) {
 		enum add_p_mode mode;
 
 		if (!patch_mode)

ci/run-build-and-tests.sh

@@ -29,7 +29,7 @@ linux-gcc)
 	export GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
 	export GIT_TEST_MULTI_PACK_INDEX_WRITE_BITMAP=1
-	export GIT_TEST_ADD_I_USE_BUILTIN=1
+	export GIT_TEST_ADD_I_USE_BUILTIN=0
 	export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master
 	export GIT_TEST_WRITE_REV_INDEX=1
 	export GIT_TEST_CHECKOUT_WORKERS=2

t/README

@@ -419,7 +419,7 @@ the --sparse command-line argument.
 GIT_TEST_PRELOAD_INDEX=<boolean> exercises the preload-index code path
 by overriding the minimum number of cache entries required per thread.
 
-GIT_TEST_ADD_I_USE_BUILTIN=<boolean>, when true, enables the
+GIT_TEST_ADD_I_USE_BUILTIN=<boolean>, when false, disables the
 built-in version of git add -i. See 'add.interactive.useBuiltin' in
 git-config(1).
 

t/t2016-checkout-patch.sh

@@ -4,7 +4,7 @@ test_description='git checkout --patch'
 
 . ./lib-patch-mode.sh
 
-if ! test_bool_env GIT_TEST_ADD_I_USE_BUILTIN false && ! test_have_prereq PERL
+if ! test_bool_env GIT_TEST_ADD_I_USE_BUILTIN true && ! test_have_prereq PERL
 then
 	skip_all='skipping interactive add tests, PERL not set'
 	test_done