[PATCH/WIP 7/8] am: apply patch with git-apply

[Paul Tan <pyokagan@gmail.com>]

Implement applying the patch to the index using git-apply.

Signed-off-by: Paul Tan <pyokagan@gmail.com>
---
 builtin/am.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/builtin/am.c b/builtin/am.c
index 0b8a42d..7126df3 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -25,6 +25,18 @@ static int is_empty_file(const char *filename)
 	return !st.st_size;
 }
 
+/**
+ * Returns the first line of msg
+ */
+static const char *firstline(const char *msg)
+{
+	static struct strbuf sb = STRBUF_INIT;
+
+	strbuf_reset(&sb);
+	strbuf_add(&sb, msg, strchrnul(msg, '\n') - msg);
+	return sb.buf;
+}
+
 enum patch_format {
 	PATCH_FORMAT_UNKNOWN = 0,
 	PATCH_FORMAT_MBOX
@@ -503,6 +515,29 @@ static int parse_patch(struct am_state *state, const char *patch)
 	return 0;
 }
 
+/*
+ * Applies current patch with git-apply. Returns 0 on success, -1 otherwise.
+ */
+static int run_apply(const struct am_state *state)
+{
+	struct child_process cp = CHILD_PROCESS_INIT;
+
+	cp.git_cmd = 1;
+
+	argv_array_push(&cp.args, "apply");
+	argv_array_push(&cp.args, "--index");
+	argv_array_push(&cp.args, am_path(state, "patch"));
+
+	if (run_command(&cp))
+		return -1;
+
+	/* Reload index as git-apply will have modified it. */
+	discard_cache();
+	read_cache();
+
+	return 0;
+}
+
 /**
  * Applies all queued patches.
  */
@@ -520,7 +555,20 @@ static void am_run(struct am_state *state)
 		write_file(am_path(state, "final-commit"), 1, "%s", state->msg.buf);
 		write_author_script(state);
 
-		/* patch application not implemented yet */
+		printf_ln(_("Applying: %s"), firstline(state->msg.buf));
+
+		if (run_apply(state) < 0) {
+			int value;
+
+			printf_ln(_("Patch failed at %s %s"), msgnum(state),
+					firstline(state->msg.buf));
+
+			if (!git_config_get_bool("advice.amworkdir", &value) && !value)
+				printf_ln(_("The copy of the patch that failed is found in: %s"),
+						am_path(state, "patch"));
+
+			exit(128);
+		}
 
 next:
 		am_next(state);
-- 
2.1.4