Merge branch 'js/diff-ni' (early part)

* 'js/diff-ni' (early part):
  diff --no-index: also imitate the exit status of diff(1)
  Fix typo: do not show name1 when name2 fails
  Teach git-diff-files the new option `--no-index`
  run_diff_{files,index}(): update calling convention.
  update-index: do not die too early in a read-only repository.
  git-status: do not be totally useless in a read-only repository.

Documentation/git-diff-files.txt

@@ -8,7 +8,7 @@ git-diff-files - Compares files in the working tree and the index
 
 SYNOPSIS
 --------
-'git-diff-files' [-q] [-0|-1|-2|-3|-c|--cc] [<common diff options>] [<path>...]
+'git-diff-files' [-q] [-0|-1|-2|-3|-c|--cc|-n|--no-index] [<common diff options>] [<path>...]
 
 DESCRIPTION
 -----------
@@ -36,6 +36,9 @@ omit diff output for unmerged entries and just show "Unmerged".
 	diff, similar to the way 'diff-tree' shows a merge
 	commit with these flags.
 
+\-n,\--no-index::
+	Compare the two given files / directories.
+
 -q::
 	Remain silent even on nonexistent files
 

Documentation/git-diff.txt

@@ -23,6 +23,10 @@ tree and the index file, or the index file and the working tree.
 	further add to the index but you still haven't.  You can
 	stage these changes by using gitlink:git-add[1].
 
+	If exactly two paths are given, and at least one is untracked,
+	compare the two files / directories. This behavior can be
+	forced by --no-index.
+
 'git-diff' [--options] --cached [<commit>] [--] [<path>...]::
 
 	This form is to view the changes you staged for the next

builtin-diff-files.c

@@ -10,42 +10,21 @@
 #include "builtin.h"
 
 static const char diff_files_usage[] =
-"git-diff-files [-q] [-0/-1/2/3 |-c|--cc] [<common diff options>] [<path>...]"
+"git-diff-files [-q] [-0/-1/2/3 |-c|--cc|-n|--no-index] [<common diff options>] [<path>...]"
 COMMON_DIFF_OPTIONS_HELP;
 
 int cmd_diff_files(int argc, const char **argv, const char *prefix)
 {
 	struct rev_info rev;
-	int silent = 0;
+	int nongit = 0;
 
+	prefix = setup_git_directory_gently(&nongit);
 	init_revisions(&rev, prefix);
 	git_config(git_default_config); /* no "diff" UI options */
 	rev.abbrev = 0;
 
 	argc = setup_revisions(argc, argv, &rev, NULL);
-	while (1 < argc && argv[1][0] == '-') {
-		if (!strcmp(argv[1], "--base"))
-			rev.max_count = 1;
-		else if (!strcmp(argv[1], "--ours"))
-			rev.max_count = 2;
-		else if (!strcmp(argv[1], "--theirs"))
-			rev.max_count = 3;
-		else if (!strcmp(argv[1], "-q"))
-			silent = 1;
-		else
-			usage(diff_files_usage);
-		argv++; argc--;
-	}
 	if (!rev.diffopt.output_format)
 		rev.diffopt.output_format = DIFF_FORMAT_RAW;
-
-	/*
-	 * Make sure there are NO revision (i.e. pending object) parameter,
-	 * rev.max_count is reasonable (0 <= n <= 3),
-	 * there is no other revision filtering parameters.
-	 */
-	if (rev.pending.nr ||
-	    rev.min_age != -1 || rev.max_age != -1)
-		usage(diff_files_usage);
-	return run_diff_files(&rev, silent);
+	return run_diff_files_cmd(&rev, argc, argv);
 }

builtin-diff-index.c

@@ -38,5 +38,9 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 	if (rev.pending.nr != 1 ||
 	    rev.max_count != -1 || rev.min_age != -1 || rev.max_age != -1)
 		usage(diff_cache_usage);
+	if (read_cache() < 0) {
+		perror("read_cache");
+		return -1;
+	}
 	return run_diff_index(&rev, cached);
 }

builtin-diff.c

@@ -25,40 +25,6 @@ struct blobinfo {
 static const char builtin_diff_usage[] =
 "git-diff <options> <rev>{0,2} -- <path>*";
 
-static int builtin_diff_files(struct rev_info *revs,
-			      int argc, const char **argv)
-{
-	int silent = 0;
-	while (1 < argc) {
-		const char *arg = argv[1];
-		if (!strcmp(arg, "--base"))
-			revs->max_count = 1;
-		else if (!strcmp(arg, "--ours"))
-			revs->max_count = 2;
-		else if (!strcmp(arg, "--theirs"))
-			revs->max_count = 3;
-		else if (!strcmp(arg, "-q"))
-			silent = 1;
-		else
-			usage(builtin_diff_usage);
-		argv++; argc--;
-	}
-	/*
-	 * Make sure there are NO revision (i.e. pending object) parameter,
-	 * specified rev.max_count is reasonable (0 <= n <= 3), and
-	 * there is no other revision filtering parameter.
-	 */
-	if (revs->pending.nr ||
-	    revs->min_age != -1 ||
-	    revs->max_age != -1 ||
-	    3 < revs->max_count)
-		usage(builtin_diff_usage);
-	if (revs->max_count < 0 &&
-	    (revs->diffopt.output_format & DIFF_FORMAT_PATCH))
-		revs->combine_merges = revs->dense_combined_merges = 1;
-	return run_diff_files(revs, silent);
-}
-
 static void stuff_change(struct diff_options *opt,
 			 unsigned old_mode, unsigned new_mode,
 			 const unsigned char *old_sha1,
@@ -151,6 +117,10 @@ static int builtin_diff_index(struct rev_info *revs,
 	    revs->max_count != -1 || revs->min_age != -1 ||
 	    revs->max_age != -1)
 		usage(builtin_diff_usage);
+	if (read_cache() < 0) {
+		perror("read_cache");
+		return -1;
+	}
 	return run_diff_index(revs, cached);
 }
 
@@ -219,6 +189,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	int ents = 0, blobs = 0, paths = 0;
 	const char *path = NULL;
 	struct blobinfo blob[2];
+	int nongit = 0;
 
 	/*
 	 * We could get N tree-ish in the rev.pending_objects list.
@@ -240,6 +211,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	 * Other cases are errors.
 	 */
 
+	prefix = setup_git_directory_gently(&nongit);
 	git_config(git_diff_ui_config);
 	init_revisions(&rev, prefix);
 
@@ -317,7 +289,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	if (!ents) {
 		switch (blobs) {
 		case 0:
-			return builtin_diff_files(&rev, argc, argv);
+			return run_diff_files_cmd(&rev, argc, argv);
 			break;
 		case 1:
 			if (paths != 1)

builtin-update-index.c

@@ -487,14 +487,17 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 	int prefix_length = prefix ? strlen(prefix) : 0;
 	char set_executable_bit = 0;
 	unsigned int refresh_flags = 0;
+	int lock_error = 0;
 	struct lock_file *lock_file;
 
 	git_config(git_default_config);
 
 	/* We can't free this memory, it becomes part of a linked list parsed atexit() */
 	lock_file = xcalloc(1, sizeof(struct lock_file));
 
-	newfd = hold_lock_file_for_update(lock_file, get_index_file(), 1);
+	newfd = hold_lock_file_for_update(lock_file, get_index_file(), 0);
+	if (newfd < 0)
+		lock_error = errno;
 
 	entries = read_cache();
 	if (entries < 0)
@@ -651,6 +654,12 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 
  finish:
 	if (active_cache_changed) {
+		if (newfd < 0) {
+			if (refresh_flags & REFRESH_QUIET)
+				exit(128);
+			die("unable to create '%s.lock': %s",
+			    get_index_file(), strerror(lock_error));
+		}
 		if (write_cache(newfd, active_cache, active_nr) ||
 		    close(newfd) || commit_lock_file(lock_file))
 			die("Unable to write new index file");