When the user runs "git add -e", the diff of the working tree changes
is written to a temporary file, opened in an editor, and then applied
back to the index. The application step is done by spawning a child
process running "git apply --recount --cached <file>", which is an
unnecessary subprocess since the apply machinery is available as a
native C API.

Replace the run_command() call with a direct call to apply_all_patches()
using an initialized apply_state with the cached and recount options set
appropriately. This avoids the overhead of forking a subprocess, keeps
the operation within the same process, and makes the intent of the code
clearer to the reader.

Remove the now-unused includes of "run-command.h" and "strvec.h" since
no other code in this file requires them after this change.

Signed-off-by: Gatla Vishweshwar Reddy <redacted>
---

Changes in v3:
- Moved struct apply_state and apply_argv declarations to the top of
  the function to fix -Wdeclaration-after-statement violations

In response to review:
- repo_git_path() returns an absolute path built from gitdir.
  prefix_filename() in apply_all_patches() explicitly skips absolute
  paths (see abspath.c lines 271-272 where is_absolute_path(arg)
  causes the prefix to be skipped). Running "git add -e" from a
  subdirectory is therefore safe.
- A dedicated test for "git add -e" from a subdirectory would be
  valuable. I looked but found no existing "add -e" tests in the test
  suite to use as a reference. I would appreciate guidance on the
  preferred approach, or I can attempt to write one if you can point
  me to a similar test pattern.

 builtin/add.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/builtin/add.c b/builtin/add.c
index c859f66519..1858adf289 100644
--- a/builtin/add.c
+++ b/builtin/add.c

@@ -13,7 +13,6 @@
 #include "dir.h"
 #include "gettext.h"
 #include "pathspec.h"
-#include "run-command.h"
 #include "object-file.h"
 #include "odb.h"
 #include "odb/transaction.h"

@@ -23,9 +22,9 @@
 #include "diff.h"
 #include "read-cache.h"
 #include "revision.h"
-#include "strvec.h"
 #include "submodule.h"
 #include "add-interactive.h"
+#include "apply.h"

 static const char * const builtin_add_usage[] = {
 	N_("git add [<options>] [--] <pathspec>..."),

@@ -187,7 +186,8 @@ static int edit_patch(struct repository *repo,
 		      const char *prefix)
 {
 	char *file = repo_git_path(repo, "ADD_EDIT.patch");
-	struct child_process child = CHILD_PROCESS_INIT;
+	struct apply_state state;
+	const char *apply_argv[2];
 	struct rev_info rev;
 	int out;
 	struct stat st;

@@ -217,11 +217,16 @@ static int edit_patch(struct repository *repo,
 	if (!st.st_size)
 		die(_("empty patch. aborted"));

-	child.git_cmd = 1;
-	strvec_pushl(&child.args, "apply", "--recount", "--cached", file,
-		     NULL);
-	if (run_command(&child))
+	apply_argv[0] = file;
+	apply_argv[1] = NULL;
+	if (init_apply_state(&state, repo, prefix))
+		die(_("could not initialize apply state"));
+	state.cached = 1;
+	if (check_apply_state(&state, 0))
+		die(_("could not check apply state"));
+	if (apply_all_patches(&state, 1, apply_argv, APPLY_OPT_RECOUNT))
 		die(_("could not apply '%s'"), file);
+	clear_apply_state(&state);

 	unlink(file);
 	free(file);
--

2.54.0