diff: move no-index detection to builtin/diff.c

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.

There are no functional changes.

Helped-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/diff.c

@@ -16,6 +16,9 @@
 #include "submodule.h"
 #include "sha1-array.h"
 
+#define DIFF_NO_INDEX_EXPLICIT 1
+#define DIFF_NO_INDEX_IMPLICIT 2
+
 struct blobinfo {
 	unsigned char sha1[20];
 	const char *name;
@@ -257,7 +260,7 @@ 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 = 0, no_index = 0;
 	int result = 0;
 
 	/*
@@ -283,14 +286,57 @@ 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 = DIFF_NO_INDEX_EXPLICIT;
+		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.
+	 */
+	if (nongit || ((argc == i + 2) &&
+		       (!path_inside_repo(prefix, argv[i]) ||
+			!path_inside_repo(prefix, argv[i + 1]))))
+		no_index = DIFF_NO_INDEX_IMPLICIT;
+
 	gitmodules_config();
 	git_config(git_diff_ui_config, NULL);
 
 	init_revisions(&rev, prefix);
 
+	if (no_index) {
+		if (argc != i + 2) {
+			if (no_index == DIFF_NO_INDEX_IMPLICIT) {
+				/*
+				 * 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 == DIFF_NO_INDEX_EXPLICIT ?
+					"--no-index" : "[--no-index]");
+
+		}
 		/* If this is a no-index diff, just run it and exit there. */
-	diff_no_index(&rev, argc, argv, nongit, prefix);
+		diff_no_index(&rev, argc, argv, prefix);
+	}
 
 	/* Otherwise, we are doing the usual "git" diff */
 	rev.diffopt.skip_stat_unmatch = !!diff_auto_refresh_index;

diff-no-index.c

@@ -183,54 +183,12 @@ 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)
+		   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.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 void diff_no_index(struct rev_info *, int, const char **, const char *);
 
 extern int index_differs_from(const char *def, int diff_flags);