[PATCH v3 1/2] diff: move no-index detection to builtin/diff.c

[Thomas Gummerer <t.gummerer@gmail.com>]

Currently the --no-index option is parsed in diff_no_index().  Move the
detection if a no-index diff should be executed to builtin/diff.c, where
we can use it for executing diff_no_index() conditionally.  This will
also allow us to execute other operations conditionally, which will be
done in the next patch.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
---

Thanks to Junio, Torsten and Eric for comments on the previous round.
I've added this refactoring patch, to avoid the partial duplication of
the logic.  I've also fixed the tests, that now use a sub-shell for
executing and fix the stray && at the end of the test.

 builtin/diff.c  | 45 ++++++++++++++++++++++++++++++++++++++++++---
 diff-no-index.c | 48 +++---------------------------------------------
 diff.h          |  2 +-
 3 files changed, 46 insertions(+), 49 deletions(-)

diff --git a/builtin/diff.c b/builtin/diff.c
index adb93a9..7220b2c 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -257,7 +257,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	int blobs = 0, paths = 0;
 	const char *path = NULL;
 	struct blobinfo blob[2];
-	int nongit;
+	int nongit, no_index = 0;
 	int result = 0;
 
 	/*
@@ -283,14 +283,53 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	 * Other cases are errors.
 	 */
 
+	/* Were we asked to do --no-index explicitly? */
+	for (i = 1; i < argc; i++) {
+		if (!strcmp(argv[i], "--")) {
+			i++;
+			break;
+		}
+		if (!strcmp(argv[i], "--no-index"))
+			no_index = 1;
+		if (argv[i][0] != '-')
+			break;
+	}
+
 	prefix = setup_git_directory_gently(&nongit);
+	/*
+	 * Treat git diff with at least one path outside of the
+	 * repo the same as if the command would have been executed
+	 * outside of a git repository.  In this case it behaves
+	 * the same way as "git diff --no-index <a> <b>", which acts
+	 * as a colourful "diff" replacement.
+	 */
+	nongit |= (argc == i + 2) && !(path_inside_repo(prefix, argv[i]) &&
+				       path_inside_repo(prefix, argv[i + 1]));
 	gitmodules_config();
 	git_config(git_diff_ui_config, NULL);
 
 	init_revisions(&rev, prefix);
 
-	/* If this is a no-index diff, just run it and exit there. */
-	diff_no_index(&rev, argc, argv, nongit, prefix);
+	if (no_index || nongit) {
+		if (argc != i + 2) {
+			if (!no_index) {
+				/*
+				 * There was no --no-index and there were not two
+				 * paths. It is possible that the user intended
+				 * to do an inside-repository operation.
+				 */
+				fprintf(stderr, "Not a git repository\n");
+				fprintf(stderr,
+					"To compare two paths outside a working tree:\n");
+			}
+			/* Give the usage message for non-repository usage and exit. */
+			usagef("git diff %s <path> <path>",
+			       no_index ? "--no-index" : "[--no-index]");
+
+		}
+		/* If this is a no-index diff, just run it and exit there. */
+		diff_no_index(&rev, argc, argv, nongit, no_index, prefix);
+	}
 
 	/* Otherwise, we are doing the usual "git" diff */
 	rev.diffopt.skip_stat_unmatch = !!diff_auto_refresh_index;
diff --git a/diff-no-index.c b/diff-no-index.c
index 00a8eef..78e3090 100644
--- a/diff-no-index.c
+++ b/diff-no-index.c
@@ -181,56 +181,14 @@ static int queue_diff(struct diff_options *o,
 	}
 }
 
-void diff_no_index(struct rev_info *revs,
-		   int argc, const char **argv,
-		   int nongit, const char *prefix)
+int diff_no_index(struct rev_info *revs,
+		  int argc, const char **argv,
+		  int nongit, int no_index, const char *prefix)
 {
 	int i, prefixlen;
-	int no_index = 0;
 	unsigned deprecated_show_diff_q_option_used = 0;
 	const char *paths[2];
 
-	/* Were we asked to do --no-index explicitly? */
-	for (i = 1; i < argc; i++) {
-		if (!strcmp(argv[i], "--")) {
-			i++;
-			break;
-		}
-		if (!strcmp(argv[i], "--no-index"))
-			no_index = 1;
-		if (argv[i][0] != '-')
-			break;
-	}
-
-	if (!no_index && !nongit) {
-		/*
-		 * Inside a git repository, without --no-index.  Only
-		 * when a path outside the repository is given,
-		 * e.g. "git diff /var/tmp/[12]", or "git diff
-		 * Makefile /var/tmp/Makefile", allow it to be used as
-		 * a colourful "diff" replacement.
-		 */
-		if ((argc != i + 2) ||
-		    (path_inside_repo(prefix, argv[i]) &&
-		     path_inside_repo(prefix, argv[i+1])))
-			return;
-	}
-	if (argc != i + 2) {
-		if (!no_index) {
-			/*
-			 * There was no --no-index and there were not two
-			 * paths. It is possible that the user intended
-			 * to do an inside-repository operation.
-			 */
-			fprintf(stderr, "Not a git repository\n");
-			fprintf(stderr,
-				"To compare two paths outside a working tree:\n");
-		}
-		/* Give the usage message for non-repository usage and exit. */
-		usagef("git diff %s <path> <path>",
-		       no_index ? "--no-index" : "[--no-index]");
-	}
-
 	diff_setup(&revs->diffopt);
 	for (i = 1; i < argc - 2; ) {
 		int j;
diff --git a/diff.h b/diff.h
index e342325..3e1828a 100644
--- a/diff.h
+++ b/diff.h
@@ -330,7 +330,7 @@ extern int diff_flush_patch_id(struct diff_options *, unsigned char *);
 
 extern int diff_result_code(struct diff_options *, int);
 
-extern void diff_no_index(struct rev_info *, int, const char **, int, const char *);
+extern int diff_no_index(struct rev_info *, int, const char **, int, int, const char *);
 
 extern int index_differs_from(const char *def, int diff_flags);
 
-- 
1.8.5.4.g8639e57