Merge branch 'pw/diff-no-index-from-named-pipes' into next

"git diff --no-index" learned to read from named pipes as if they
were regular files, to allow "git diff <(process) <(substitution)"
some shells support.

* pw/diff-no-index-from-named-pipes:
  diff --no-index: support reading from named pipes
  t4054: test diff --no-index with stdin
  diff --no-index: die on error reading stdin
  diff --no-index: refuse to compare stdin to a directory

diff-no-index.c

@@ -41,42 +41,81 @@ static int read_directory_contents(const char *path, struct string_list *list)
  */
 static const char file_from_standard_input[] = "-";
 
-static int get_mode(const char *path, int *mode)
+/*
+ * For paths given on the command-line we treat "-" as stdin and named
+ * pipes and symbolic links to named pipes specially.
+ */
+enum special {
+	SPECIAL_NONE,
+	SPECIAL_STDIN,
+	SPECIAL_PIPE,
+};
+
+static int get_mode(const char *path, int *mode, enum special *special)
 {
 	struct stat st;
 
-	if (!path || !strcmp(path, "/dev/null"))
+	if (!path || !strcmp(path, "/dev/null")) {
 		*mode = 0;
 #ifdef GIT_WINDOWS_NATIVE
-	else if (!strcasecmp(path, "nul"))
+	} else if (!strcasecmp(path, "nul")) {
 		*mode = 0;
 #endif
-	else if (path == file_from_standard_input)
+	} else if (path == file_from_standard_input) {
 		*mode = create_ce_mode(0666);
-	else if (lstat(path, &st))
+		*special = SPECIAL_STDIN;
+	} else if (lstat(path, &st)) {
 		return error("Could not access '%s'", path);
-	else
+	} else {
 		*mode = st.st_mode;
+	}
+	/*
+	 * For paths on the command-line treat named pipes and symbolic
+	 * links that resolve to a named pipe specially.
+	 */
+	if (special &&
+	    (S_ISFIFO(*mode) ||
+	     (S_ISLNK(*mode) && !stat(path, &st) && S_ISFIFO(st.st_mode)))) {
+		*mode = create_ce_mode(0666);
+		*special = SPECIAL_PIPE;
+	}
+
 	return 0;
 }
 
-static int populate_from_stdin(struct diff_filespec *s)
+static void populate_common(struct diff_filespec *s, struct strbuf *buf)
 {
-	struct strbuf buf = STRBUF_INIT;
 	size_t size = 0;
 
-	if (strbuf_read(&buf, 0, 0) < 0)
-		return error_errno("error while reading from stdin");
-
 	s->should_munmap = 0;
-	s->data = strbuf_detach(&buf, &size);
+	s->data = strbuf_detach(buf, &size);
 	s->size = size;
 	s->should_free = 1;
 	s->is_stdin = 1;
-	return 0;
 }
 
-static struct diff_filespec *noindex_filespec(const char *name, int mode)
+static void populate_from_pipe(struct diff_filespec *s)
+{
+	struct strbuf buf = STRBUF_INIT;
+	int fd = xopen(s->path, O_RDONLY);
+
+	if (strbuf_read(&buf, fd, 0) < 0)
+		die_errno("error while reading from '%s'", s->path);
+	close(fd);
+	populate_common(s, &buf);
+}
+
+static void populate_from_stdin(struct diff_filespec *s)
+{
+	struct strbuf buf = STRBUF_INIT;
+
+	if (strbuf_read(&buf, 0, 0) < 0)
+		die_errno("error while reading from stdin");
+	populate_common(s, &buf);
+}
+
+static struct diff_filespec *noindex_filespec(const char *name, int mode,
+					      enum special special)
 {
 	struct diff_filespec *s;
 
@@ -84,17 +123,22 @@ static struct diff_filespec *noindex_filespec(const char *name, int mode)
 		name = "/dev/null";
 	s = alloc_filespec(name);
 	fill_filespec(s, null_oid(), 0, mode);
-	if (name == file_from_standard_input)
+	if (special == SPECIAL_STDIN)
 		populate_from_stdin(s);
+	else if (special == SPECIAL_PIPE)
+		populate_from_pipe(s);
 	return s;
 }
 
 static int queue_diff(struct diff_options *o,
-		      const char *name1, const char *name2)
+		      const char *name1, const char *name2, int recursing)
 {
 	int mode1 = 0, mode2 = 0;
+	enum special special1 = SPECIAL_NONE, special2 = SPECIAL_NONE;
 
-	if (get_mode(name1, &mode1) || get_mode(name2, &mode2))
+	/* Paths can only be special if we're not recursing. */
+	if (get_mode(name1, &mode1, recursing ? NULL : &special1) ||
+	    get_mode(name2, &mode2, recursing ? NULL : &special2))
 		return -1;
 
 	if (mode1 && mode2 && S_ISDIR(mode1) != S_ISDIR(mode2)) {
@@ -102,14 +146,14 @@ static int queue_diff(struct diff_options *o,
 
 		if (S_ISDIR(mode1)) {
 			/* 2 is file that is created */
-			d1 = noindex_filespec(NULL, 0);
+			d1 = noindex_filespec(NULL, 0, SPECIAL_NONE);
-			d2 = noindex_filespec(name2, mode2);
+			d2 = noindex_filespec(name2, mode2, special2);
 			name2 = NULL;
 			mode2 = 0;
 		} else {
 			/* 1 is file that is deleted */
-			d1 = noindex_filespec(name1, mode1);
+			d1 = noindex_filespec(name1, mode1, special1);
-			d2 = noindex_filespec(NULL, 0);
+			d2 = noindex_filespec(NULL, 0, SPECIAL_NONE);
 			name1 = NULL;
 			mode1 = 0;
 		}
@@ -174,7 +218,7 @@ static int queue_diff(struct diff_options *o,
 				n2 = buffer2.buf;
 			}
 
-			ret = queue_diff(o, n1, n2);
+			ret = queue_diff(o, n1, n2, 1);
 		}
 		string_list_clear(&p1, 0);
 		string_list_clear(&p2, 0);
@@ -190,8 +234,8 @@ static int queue_diff(struct diff_options *o,
 			SWAP(name1, name2);
 		}
 
-		d1 = noindex_filespec(name1, mode1);
+		d1 = noindex_filespec(name1, mode1, special1);
-		d2 = noindex_filespec(name2, mode2);
+		d2 = noindex_filespec(name2, mode2, special2);
 		diff_queue(&diff_queued_diff, d1, d2);
 		return 0;
 	}
@@ -216,13 +260,27 @@ static void append_basename(struct strbuf *path, const char *dir, const char *fi
  */
 static void fixup_paths(const char **path, struct strbuf *replacement)
 {
-	unsigned int isdir0, isdir1;
+	struct stat st;
+	unsigned int isdir0 = 0, isdir1 = 0;
+	unsigned int ispipe0 = 0, ispipe1 = 0;
+
+	if (path[0] != file_from_standard_input && !stat(path[0], &st)) {
+		isdir0 = S_ISDIR(st.st_mode);
+		ispipe0 = S_ISFIFO(st.st_mode);
+	}
+
+	if (path[1] != file_from_standard_input && !stat(path[1], &st)) {
+		isdir1 = S_ISDIR(st.st_mode);
+		ispipe1 = S_ISFIFO(st.st_mode);
+	}
+
+	if ((path[0] == file_from_standard_input && isdir1) ||
+	    (isdir0 && path[1] == file_from_standard_input))
+		die(_("cannot compare stdin to a directory"));
+
+	if ((isdir0 && ispipe1) || (ispipe0 && isdir1))
+		die(_("cannot compare a named pipe to a directory"));
 
-	if (path[0] == file_from_standard_input ||
-	    path[1] == file_from_standard_input)
-		return;
-	isdir0 = is_directory(path[0]);
-	isdir1 = is_directory(path[1]);
 	if (isdir0 == isdir1)
 		return;
 	if (isdir0) {
@@ -296,7 +354,7 @@ int diff_no_index(struct rev_info *revs,
 	setup_diff_pager(&revs->diffopt);
 	revs->diffopt.flags.exit_with_status = 1;
 
-	if (queue_diff(&revs->diffopt, paths[0], paths[1]))
+	if (queue_diff(&revs->diffopt, paths[0], paths[1], 0))
 		goto out;
 	diff_set_mnemonic_prefix(&revs->diffopt, "1/", "2/");
 	diffcore_std(&revs->diffopt);

t/t4053-diff-no-index.sh

@@ -205,4 +205,68 @@ test_expect_success POSIXPERM,SYMLINKS 'diff --no-index normalizes: mode not lik
 	test_cmp expected actual
 '
 
+test_expect_success "diff --no-index treats '-' as stdin" '
+	cat >expect <<-EOF &&
+	diff --git a/- b/a/1
+	index $ZERO_OID..$(git hash-object --stdin <a/1) 100644
+	--- a/-
+	+++ b/a/1
+	@@ -1 +1 @@
+	-x
+	+1
+	EOF
+
+	test_write_lines x | test_expect_code 1 \
+		git -c core.abbrev=no diff --no-index -- - a/1 >actual &&
+	test_cmp expect actual &&
+
+	test_write_lines 1 | git diff --no-index -- a/1 - >actual &&
+	test_must_be_empty actual
+'
+
+test_expect_success 'diff --no-index refuses to diff stdin and a directory' '
+	test_must_fail git diff --no-index -- - a </dev/null 2>err &&
+	grep "fatal: cannot compare stdin to a directory" err
+'
+
+test_expect_success PIPE 'diff --no-index refuses to diff a named pipe and a directory' '
+	test_when_finished "rm -f pipe" &&
+	mkfifo pipe &&
+	{
+		(>pipe) &
+	} &&
+	test_when_finished "kill $!" &&
+	test_must_fail git diff --no-index -- pipe a 2>err &&
+	grep "fatal: cannot compare a named pipe to a directory" err
+'
+
+test_expect_success PIPE,SYMLINKS 'diff --no-index reads from pipes' '
+	test_when_finished "rm -f old new new-link" &&
+	mkfifo old &&
+	mkfifo new &&
+	ln -s new new-link &&
+	{
+		(test_write_lines a b c >old) &
+	} &&
+	test_when_finished "! kill $!" &&
+	{
+		(test_write_lines a x c >new) &
+	} &&
+	test_when_finished "! kill $!" &&
+
+	cat >expect <<-EOF &&
+	diff --git a/old b/new-link
+	--- a/old
+	+++ b/new-link
+	@@ -1,3 +1,3 @@
+	 a
+	-b
+	+x
+	 c
+	EOF
+
+	test_expect_code 1 git diff --no-index old new-link >actual &&
+	test_cmp expect actual
+'
+
 test_done