Merge branch 'tg/rerere'

Fixes to "git rerere" corner cases, especially when conflict
markers cannot be parsed in the file.

* tg/rerere:
  rerere: recalculate conflict ID when unresolved conflict is committed
  rerere: teach rerere to handle nested conflicts
  rerere: return strbuf from handle path
  rerere: factor out handle_conflict function
  rerere: only return whether a path has conflicts or not
  rerere: fix crash with files rerere can't handle
  rerere: add documentation for conflict normalization
  rerere: mark strings for translation
  rerere: wrap paths in output in sq
  rerere: lowercase error messages
  rerere: unify error messages when read_cache fails

Documentation/technical/rerere.txt

@@ -0,0 +1,182 @@
+Rerere
+======
+
+This document describes the rerere logic.
+
+Conflict normalization
+----------------------
+
+To ensure recorded conflict resolutions can be looked up in the rerere
+database, even when branches are merged in a different order,
+different branches are merged that result in the same conflict, or
+when different conflict style settings are used, rerere normalizes the
+conflicts before writing them to the rerere database.
+
+Different conflict styles and branch names are normalized by stripping
+the labels from the conflict markers, and removing the common ancestor
+version from the `diff3` conflict style. Branches that are merged
+in different order are normalized by sorting the conflict hunks.  More
+on each of those steps in the following sections.
+
+Once these two normalization operations are applied, a conflict ID is
+calculated based on the normalized conflict, which is later used by
+rerere to look up the conflict in the rerere database.
+
+Removing the common ancestor version
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Say we have three branches AB, AC and AC2.  The common ancestor of
+these branches has a file with a line containing the string "A" (for
+brevity this is called "line A" in the rest of the document).  In
+branch AB this line is changed to "B", in AC, this line is changed to
+"C", and branch AC2 is forked off of AC, after the line was changed to
+"C".
+
+Forking a branch ABAC off of branch AB and then merging AC into it, we
+get a conflict like the following:
+
+    <<<<<<< HEAD
+    B
+    =======
+    C
+    >>>>>>> AC
+
+Doing the analogous with AC2 (forking a branch ABAC2 off of branch AB
+and then merging branch AC2 into it), using the diff3 conflict style,
+we get a conflict like the following:
+
+    <<<<<<< HEAD
+    B
+    ||||||| merged common ancestors
+    A
+    =======
+    C
+    >>>>>>> AC2
+
+By resolving this conflict, to leave line D, the user declares:
+
+    After examining what branches AB and AC did, I believe that making
+    line A into line D is the best thing to do that is compatible with
+    what AB and AC wanted to do.
+
+As branch AC2 refers to the same commit as AC, the above implies that
+this is also compatible what AB and AC2 wanted to do.
+
+By extension, this means that rerere should recognize that the above
+conflicts are the same.  To do this, the labels on the conflict
+markers are stripped, and the common ancestor version is removed.  The above
+examples would both result in the following normalized conflict:
+
+    <<<<<<<
+    B
+    =======
+    C
+    >>>>>>>
+
+Sorting hunks
+~~~~~~~~~~~~~
+
+As before, lets imagine that a common ancestor had a file with line A
+its early part, and line X in its late part.  And then four branches
+are forked that do these things:
+
+    - AB: changes A to B
+    - AC: changes A to C
+    - XY: changes X to Y
+    - XZ: changes X to Z
+
+Now, forking a branch ABAC off of branch AB and then merging AC into
+it, and forking a branch ACAB off of branch AC and then merging AB
+into it, would yield the conflict in a different order.  The former
+would say "A became B or C, what now?" while the latter would say "A
+became C or B, what now?"
+
+As a reminder, the act of merging AC into ABAC and resolving the
+conflict to leave line D means that the user declares:
+
+    After examining what branches AB and AC did, I believe that
+    making line A into line D is the best thing to do that is
+    compatible with what AB and AC wanted to do.
+
+So the conflict we would see when merging AB into ACAB should be
+resolved the same way---it is the resolution that is in line with that
+declaration.
+
+Imagine that similarly previously a branch XYXZ was forked from XY,
+and XZ was merged into it, and resolved "X became Y or Z" into "X
+became W".
+
+Now, if a branch ABXY was forked from AB and then merged XY, then ABXY
+would have line B in its early part and line Y in its later part.
+Such a merge would be quite clean.  We can construct 4 combinations
+using these four branches ((AB, AC) x (XY, XZ)).
+
+Merging ABXY and ACXZ would make "an early A became B or C, a late X
+became Y or Z" conflict, while merging ACXY and ABXZ would make "an
+early A became C or B, a late X became Y or Z".  We can see there are
+4 combinations of ("B or C", "C or B") x ("X or Y", "Y or X").
+
+By sorting, the conflict is given its canonical name, namely, "an
+early part became B or C, a late part becames X or Y", and whenever
+any of these four patterns appear, and we can get to the same conflict
+and resolution that we saw earlier.
+
+Without the sorting, we'd have to somehow find a previous resolution
+from combinatorial explosion.
+
+Conflict ID calculation
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Once the conflict normalization is done, the conflict ID is calculated
+as the sha1 hash of the conflict hunks appended to each other,
+separated by <NUL> characters.  The conflict markers are stripped out
+before the sha1 is calculated.  So in the example above, where we
+merge branch AC which changes line A to line C, into branch AB, which
+changes line A to line C, the conflict ID would be
+SHA1('B<NUL>C<NUL>').
+
+If there are multiple conflicts in one file, the sha1 is calculated
+the same way with all hunks appended to each other, in the order in
+which they appear in the file, separated by a <NUL> character.
+
+Nested conflicts
+~~~~~~~~~~~~~~~~
+
+Nested conflicts are handled very similarly to "simple" conflicts.
+Similar to simple conflicts, the conflict is first normalized by
+stripping the labels from conflict markers, stripping the common ancestor
+version, and the sorting the conflict hunks, both for the outer and the
+inner conflict.  This is done recursively, so any number of nested
+conflicts can be handled.
+
+The only difference is in how the conflict ID is calculated.  For the
+inner conflict, the conflict markers themselves are not stripped out
+before calculating the sha1.
+
+Say we have the following conflict for example:
+
+    <<<<<<< HEAD
+    1
+    =======
+    <<<<<<< HEAD
+    3
+    =======
+    2
+    >>>>>>> branch-2
+    >>>>>>> branch-3~
+
+After stripping out the labels of the conflict markers, and sorting
+the hunks, the conflict would look as follows:
+
+    <<<<<<<
+    1
+    =======
+    <<<<<<<
+    2
+    =======
+    3
+    >>>>>>>
+    >>>>>>>
+
+and finally the conflict ID would be calculated as:
+`sha1('1<NUL><<<<<<<\n3\n=======\n2\n>>>>>>><NUL>')`

builtin/rerere.c

@@ -75,7 +75,7 @@ int cmd_rerere(int argc, const char **argv, const char *prefix)
 	if (!strcmp(argv[0], "forget")) {
 		struct pathspec pathspec;
 		if (argc < 2)
-			warning("'git rerere forget' without paths is deprecated");
+			warning(_("'git rerere forget' without paths is deprecated"));
 		parse_pathspec(&pathspec, 0, PATHSPEC_PREFER_CWD,
 			       prefix, argv + 1);
 		return rerere_forget(&pathspec);
@@ -107,7 +107,7 @@ int cmd_rerere(int argc, const char **argv, const char *prefix)
 			const char *path = merge_rr.items[i].string;
 			const struct rerere_id *id = merge_rr.items[i].util;
 			if (diff_two(rerere_path(id, "preimage"), path, path, path))
-				die("unable to generate diff for %s", rerere_path(id, NULL));
+				die(_("unable to generate diff for '%s'"), rerere_path(id, NULL));
 		}
 	} else
 		usage_with_options(rerere_usage, options);

rerere.c

@@ -213,7 +213,7 @@ static void read_rr(struct string_list *rr)
 
 		/* There has to be the hash, tab, path and then NUL */
 		if (buf.len < 42 || get_sha1_hex(buf.buf, sha1))
-			die("corrupt MERGE_RR");
+			die(_("corrupt MERGE_RR"));
 
 		if (buf.buf[40] != '.') {
 			variant = 0;
@@ -222,10 +222,10 @@ static void read_rr(struct string_list *rr)
 			errno = 0;
 			variant = strtol(buf.buf + 41, &path, 10);
 			if (errno)
-				die("corrupt MERGE_RR");
+				die(_("corrupt MERGE_RR"));
 		}
 		if (*(path++) != '\t')
-			die("corrupt MERGE_RR");
+			die(_("corrupt MERGE_RR"));
 		buf.buf[40] = '\0';
 		id = new_rerere_id_hex(buf.buf);
 		id->variant = variant;
@@ -260,12 +260,12 @@ static int write_rr(struct string_list *rr, int out_fd)
 				    rr->items[i].string, 0);
 
 		if (write_in_full(out_fd, buf.buf, buf.len) < 0)
-			die("unable to write rerere record");
+			die(_("unable to write rerere record"));
 
 		strbuf_release(&buf);
 	}
 	if (commit_lock_file(&write_lock) != 0)
-		die("unable to write rerere record");
+		die(_("unable to write rerere record"));
 	return 0;
 }
 
@@ -303,38 +303,6 @@ static void rerere_io_putstr(const char *str, struct rerere_io *io)
 		ferr_puts(str, io->output, &io->wrerror);
 }
 
-/*
- * Write a conflict marker to io->output (if defined).
- */
-static void rerere_io_putconflict(int ch, int size, struct rerere_io *io)
-{
-	char buf[64];
-
-	while (size) {
-		if (size <= sizeof(buf) - 2) {
-			memset(buf, ch, size);
-			buf[size] = '\n';
-			buf[size + 1] = '\0';
-			size = 0;
-		} else {
-			int sz = sizeof(buf) - 1;
-
-			/*
-			 * Make sure we will not write everything out
-			 * in this round by leaving at least 1 byte
-			 * for the next round, giving the next round
-			 * a chance to add the terminating LF.  Yuck.
-			 */
-			if (size <= sz)
-				sz -= (sz - size) + 1;
-			memset(buf, ch, sz);
-			buf[sz] = '\0';
-			size -= sz;
-		}
-		rerere_io_putstr(buf, io);
-	}
-}
-
 static void rerere_io_putmem(const char *mem, size_t sz, struct rerere_io *io)
 {
 	if (io->output)
@@ -385,6 +353,71 @@ static int is_cmarker(char *buf, int marker_char, int marker_size)
 	return isspace(*buf);
 }
 
+static void rerere_strbuf_putconflict(struct strbuf *buf, int ch, size_t size)
+{
+	strbuf_addchars(buf, ch, size);
+	strbuf_addch(buf, '\n');
+}
+
+static int handle_conflict(struct strbuf *out, struct rerere_io *io,
+			   int marker_size, git_SHA_CTX *ctx)
+{
+	enum {
+		RR_SIDE_1 = 0, RR_SIDE_2, RR_ORIGINAL
+	} hunk = RR_SIDE_1;
+	struct strbuf one = STRBUF_INIT, two = STRBUF_INIT;
+	struct strbuf buf = STRBUF_INIT, conflict = STRBUF_INIT;
+	int has_conflicts = -1;
+
+	while (!io->getline(&buf, io)) {
+		if (is_cmarker(buf.buf, '<', marker_size)) {
+			if (handle_conflict(&conflict, io, marker_size, NULL) < 0)
+				break;
+			if (hunk == RR_SIDE_1)
+				strbuf_addbuf(&one, &conflict);
+			else
+				strbuf_addbuf(&two, &conflict);
+			strbuf_release(&conflict);
+		} else if (is_cmarker(buf.buf, '|', marker_size)) {
+			if (hunk != RR_SIDE_1)
+				break;
+			hunk = RR_ORIGINAL;
+		} else if (is_cmarker(buf.buf, '=', marker_size)) {
+			if (hunk != RR_SIDE_1 && hunk != RR_ORIGINAL)
+				break;
+			hunk = RR_SIDE_2;
+		} else if (is_cmarker(buf.buf, '>', marker_size)) {
+			if (hunk != RR_SIDE_2)
+				break;
+			if (strbuf_cmp(&one, &two) > 0)
+				strbuf_swap(&one, &two);
+			has_conflicts = 1;
+			rerere_strbuf_putconflict(out, '<', marker_size);
+			strbuf_addbuf(out, &one);
+			rerere_strbuf_putconflict(out, '=', marker_size);
+			strbuf_addbuf(out, &two);
+			rerere_strbuf_putconflict(out, '>', marker_size);
+			if (ctx) {
+				git_SHA1_Update(ctx, one.buf ? one.buf : "",
+					    one.len + 1);
+				git_SHA1_Update(ctx, two.buf ? two.buf : "",
+					    two.len + 1);
+			}
+			break;
+		} else if (hunk == RR_SIDE_1)
+			strbuf_addbuf(&one, &buf);
+		else if (hunk == RR_ORIGINAL)
+			; /* discard */
+		else if (hunk == RR_SIDE_2)
+			strbuf_addbuf(&two, &buf);
+	}
+	strbuf_release(&one);
+	strbuf_release(&two);
+	strbuf_release(&buf);
+
+	return has_conflicts;
+}
+
 /*
  * Read contents a file with conflicts, normalize the conflicts
  * by (1) discarding the common ancestor version in diff3-style,
@@ -394,80 +427,35 @@ static int is_cmarker(char *buf, int marker_char, int marker_size)
  * one side of the conflict, NUL, the other side of the conflict,
  * and NUL concatenated together.
  *
- * Return the number of conflict hunks found.
- *
- * NEEDSWORK: the logic and theory of operation behind this conflict
- * normalization may deserve to be documented somewhere, perhaps in
- * Documentation/technical/rerere.txt.
+ * Return 1 if conflict hunks are found, 0 if there are no conflict
+ * hunks and -1 if an error occured.
  */
 static int handle_path(unsigned char *sha1, struct rerere_io *io, int marker_size)
 {
 	git_SHA_CTX ctx;
-	int hunk_no = 0;
-	enum {
-		RR_CONTEXT = 0, RR_SIDE_1, RR_SIDE_2, RR_ORIGINAL
-	} hunk = RR_CONTEXT;
-	struct strbuf one = STRBUF_INIT, two = STRBUF_INIT;
-	struct strbuf buf = STRBUF_INIT;
-
+	struct strbuf buf = STRBUF_INIT, out = STRBUF_INIT;
+	int has_conflicts = 0;
 	if (sha1)
 		git_SHA1_Init(&ctx);
 
 	while (!io->getline(&buf, io)) {
 		if (is_cmarker(buf.buf, '<', marker_size)) {
-			if (hunk != RR_CONTEXT)
-				goto bad;
-			hunk = RR_SIDE_1;
-		} else if (is_cmarker(buf.buf, '|', marker_size)) {
-			if (hunk != RR_SIDE_1)
-				goto bad;
-			hunk = RR_ORIGINAL;
-		} else if (is_cmarker(buf.buf, '=', marker_size)) {
-			if (hunk != RR_SIDE_1 && hunk != RR_ORIGINAL)
-				goto bad;
-			hunk = RR_SIDE_2;
-		} else if (is_cmarker(buf.buf, '>', marker_size)) {
-			if (hunk != RR_SIDE_2)
-				goto bad;
-			if (strbuf_cmp(&one, &two) > 0)
-				strbuf_swap(&one, &two);
-			hunk_no++;
-			hunk = RR_CONTEXT;
-			rerere_io_putconflict('<', marker_size, io);
-			rerere_io_putmem(one.buf, one.len, io);
-			rerere_io_putconflict('=', marker_size, io);
-			rerere_io_putmem(two.buf, two.len, io);
-			rerere_io_putconflict('>', marker_size, io);
-			if (sha1) {
-				git_SHA1_Update(&ctx, one.buf ? one.buf : "",
-					    one.len + 1);
-				git_SHA1_Update(&ctx, two.buf ? two.buf : "",
-					    two.len + 1);
-			}
-			strbuf_reset(&one);
-			strbuf_reset(&two);
-		} else if (hunk == RR_SIDE_1)
-			strbuf_addbuf(&one, &buf);
-		else if (hunk == RR_ORIGINAL)
-			; /* discard */
-		else if (hunk == RR_SIDE_2)
-			strbuf_addbuf(&two, &buf);
-		else
+			has_conflicts = handle_conflict(&out, io, marker_size,
+							sha1 ? &ctx : NULL);
+			if (has_conflicts < 0)
+				break;
+			rerere_io_putmem(out.buf, out.len, io);
+			strbuf_reset(&out);
+		} else
 			rerere_io_putstr(buf.buf, io);
-		continue;
-	bad:
-		hunk = 99; /* force error exit */
-		break;
 	}
-	strbuf_release(&one);
-	strbuf_release(&two);
 	strbuf_release(&buf);
+	strbuf_release(&out);
 
 	if (sha1)
 		git_SHA1_Final(sha1, &ctx);
-	if (hunk != RR_CONTEXT)
-		return -1;
-	return hunk_no;
+
+	return has_conflicts;
 }
 
 /*
@@ -476,7 +464,7 @@ static int handle_path(unsigned char *sha1, struct rerere_io *io, int marker_siz
  */
 static int handle_file(const char *path, unsigned char *sha1, const char *output)
 {
-	int hunk_no = 0;
+	int has_conflicts = 0;
 	struct rerere_io_file io;
 	int marker_size = ll_merge_marker_size(path);
 
@@ -485,34 +473,34 @@ static int handle_file(const char *path, unsigned char *sha1, const char *output
 	io.input = fopen(path, "r");
 	io.io.wrerror = 0;
 	if (!io.input)
-		return error_errno("Could not open %s", path);
+		return error_errno(_("could not open '%s'"), path);
 
 	if (output) {
 		io.io.output = fopen(output, "w");
 		if (!io.io.output) {
-			error_errno("Could not write %s", output);
+			error_errno(_("could not write '%s'"), output);
 			fclose(io.input);
 			return -1;
 		}
 	}
 
-	hunk_no = handle_path(sha1, (struct rerere_io *)&io, marker_size);
+	has_conflicts = handle_path(sha1, (struct rerere_io *)&io, marker_size);
 
 	fclose(io.input);
 	if (io.io.wrerror)
-		error("There were errors while writing %s (%s)",
+		error(_("there were errors while writing '%s' (%s)"),
 		      path, strerror(io.io.wrerror));
 	if (io.io.output && fclose(io.io.output))
-		io.io.wrerror = error_errno("Failed to flush %s", path);
+		io.io.wrerror = error_errno(_("failed to flush '%s'"), path);
 
-	if (hunk_no < 0) {
+	if (has_conflicts < 0) {
 		if (output)
 			unlink_or_warn(output);
-		return error("Could not parse conflict hunks in %s", path);
+		return error(_("could not parse conflict hunks in '%s'"), path);
 	}
 	if (io.io.wrerror)
 		return -1;
-	return hunk_no;
+	return has_conflicts;
 }
 
 /*
@@ -569,7 +557,7 @@ static int find_conflict(struct string_list *conflict)
 {
 	int i;
 	if (read_cache() < 0)
-		return error("Could not read index");
+		return error(_("index file corrupt"));
 
 	for (i = 0; i < active_nr;) {
 		int conflict_type;
@@ -602,7 +590,7 @@ int rerere_remaining(struct string_list *merge_rr)
 	if (setup_rerere(merge_rr, RERERE_READONLY))
 		return 0;
 	if (read_cache() < 0)
-		return error("Could not read index");
+		return error(_("index file corrupt"));
 
 	for (i = 0; i < active_nr;) {
 		int conflict_type;
@@ -685,17 +673,17 @@ static int merge(const struct rerere_id *id, const char *path)
 	 * Mark that "postimage" was used to help gc.
 	 */
 	if (utime(rerere_path(id, "postimage"), NULL) < 0)
-		warning_errno("failed utime() on %s",
+		warning_errno(_("failed utime() on '%s'"),
 			      rerere_path(id, "postimage"));
 
 	/* Update "path" with the resolution */
 	f = fopen(path, "w");
 	if (!f)
-		return error_errno("Could not open %s", path);
+		return error_errno(_("could not open '%s'"), path);
 	if (fwrite(result.ptr, result.size, 1, f) != 1)
-		error_errno("Could not write %s", path);
+		error_errno(_("could not write '%s'"), path);
 	if (fclose(f))
-		return error_errno("Writing %s failed", path);
+		return error_errno(_("writing '%s' failed"), path);
 
 out:
 	free(cur.ptr);
@@ -715,13 +703,13 @@ static void update_paths(struct string_list *update)
 		struct string_list_item *item = &update->items[i];
 		if (add_file_to_cache(item->string, 0))
 			exit(128);
-		fprintf(stderr, "Staged '%s' using previous resolution.\n",
+		fprintf_ln(stderr, _("Staged '%s' using previous resolution."),
 			item->string);
 	}
 
 	if (write_locked_index(&the_index, &index_lock,
 			       COMMIT_LOCK | SKIP_IF_UNCHANGED))
-		die("Unable to write new index file");
+		die(_("unable to write new index file"));
 }
 
 static void remove_variant(struct rerere_id *id)
@@ -753,7 +741,7 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 		if (!handle_file(path, NULL, NULL)) {
 			copy_file(rerere_path(id, "postimage"), path, 0666);
 			id->collection->status[variant] |= RR_HAS_POSTIMAGE;
-			fprintf(stderr, "Recorded resolution for '%s'.\n", path);
+			fprintf_ln(stderr, _("Recorded resolution for '%s'."), path);
 			free_rerere_id(rr_item);
 			rr_item->util = NULL;
 			return;
@@ -787,9 +775,9 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 		if (rerere_autoupdate)
 			string_list_insert(update, path);
 		else
-			fprintf(stderr,
-				"Resolved '%s' using previous resolution.\n",
-				path);
+			fprintf_ln(stderr,
+				   _("Resolved '%s' using previous resolution."),
+				   path);
 		free_rerere_id(rr_item);
 		rr_item->util = NULL;
 		return;
@@ -803,11 +791,11 @@ static void do_rerere_one_path(struct string_list_item *rr_item,
 	if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
 		const char *path = rerere_path(id, "postimage");
 		if (unlink(path))
-			die_errno("cannot unlink stray '%s'", path);
+			die_errno(_("cannot unlink stray '%s'"), path);
 		id->collection->status[variant] &= ~RR_HAS_POSTIMAGE;
 	}
 	id->collection->status[variant] |= RR_HAS_PREIMAGE;
-	fprintf(stderr, "Recorded preimage for '%s'\n", path);
+	fprintf_ln(stderr, _("Recorded preimage for '%s'"), path);
 }
 
 static int do_plain_rerere(struct string_list *rr, int fd)
@@ -830,15 +818,16 @@ static int do_plain_rerere(struct string_list *rr, int fd)
 		const char *path = conflict.items[i].string;
 		int ret;
 
-		if (string_list_has_string(rr, path))
-			continue;
-
 		/*
 		 * Ask handle_file() to scan and assign a
 		 * conflict ID.  No need to write anything out
 		 * yet.
 		 */
 		ret = handle_file(path, sha1, NULL);
+		if (ret != 0 && string_list_has_string(rr, path)) {
+			remove_variant(string_list_lookup(rr, path)->util);
+			string_list_remove(rr, path, 1);
+		}
 		if (ret < 1)
 			continue;
 
@@ -879,7 +868,7 @@ static int is_rerere_enabled(void)
 		return rr_cache_exists;
 
 	if (!rr_cache_exists && mkdir_in_gitdir(git_path_rr_cache()))
-		die("Could not create directory %s", git_path_rr_cache());
+		die(_("could not create directory '%s'"), git_path_rr_cache());
 	return 1;
 }
 
@@ -958,7 +947,7 @@ static int handle_cache(const char *path, unsigned char *sha1, const char *outpu
 	mmfile_t mmfile[3] = {{NULL}};
 	mmbuffer_t result = {NULL, 0};
 	const struct cache_entry *ce;
-	int pos, len, i, hunk_no;
+	int pos, len, i, has_conflicts;
 	struct rerere_io_mem io;
 	int marker_size = ll_merge_marker_size(path);
 
@@ -1012,11 +1001,11 @@ static int handle_cache(const char *path, unsigned char *sha1, const char *outpu
 	 * Grab the conflict ID and optionally write the original
 	 * contents with conflict markers out.
 	 */
-	hunk_no = handle_path(sha1, (struct rerere_io *)&io, marker_size);
+	has_conflicts = handle_path(sha1, (struct rerere_io *)&io, marker_size);
 	strbuf_release(&io.input);
 	if (io.io.output)
 		fclose(io.io.output);
-	return hunk_no;
+	return has_conflicts;
 }
 
 static int rerere_forget_one_path(const char *path, struct string_list *rr)
@@ -1033,7 +1022,7 @@ static int rerere_forget_one_path(const char *path, struct string_list *rr)
 	 */
 	ret = handle_cache(path, sha1, NULL);
 	if (ret < 1)
-		return error("Could not parse conflict hunks in '%s'", path);
+		return error(_("could not parse conflict hunks in '%s'"), path);
 
 	/* Nuke the recorded resolution for the conflict */
 	id = new_rerere_id(sha1);
@@ -1051,7 +1040,7 @@ static int rerere_forget_one_path(const char *path, struct string_list *rr)
 		handle_cache(path, sha1, rerere_path(id, "thisimage"));
 		if (read_mmfile(&cur, rerere_path(id, "thisimage"))) {
 			free(cur.ptr);
-			error("Failed to update conflicted state in '%s'", path);
+			error(_("failed to update conflicted state in '%s'"), path);
 			goto fail_exit;
 		}
 		cleanly_resolved = !try_merge(id, path, &cur, &result);
@@ -1062,16 +1051,16 @@ static int rerere_forget_one_path(const char *path, struct string_list *rr)
 	}
 
 	if (id->collection->status_nr <= id->variant) {
-		error("no remembered resolution for '%s'", path);
+		error(_("no remembered resolution for '%s'"), path);
 		goto fail_exit;
 	}
 
 	filename = rerere_path(id, "postimage");
 	if (unlink(filename)) {
 		if (errno == ENOENT)
-			error("no remembered resolution for %s", path);
+			error(_("no remembered resolution for '%s'"), path);
 		else
-			error_errno("cannot unlink %s", filename);
+			error_errno(_("cannot unlink '%s'"), filename);
 		goto fail_exit;
 	}
 
@@ -1081,7 +1070,7 @@ static int rerere_forget_one_path(const char *path, struct string_list *rr)
 	 * the postimage.
 	 */
 	handle_cache(path, sha1, rerere_path(id, "preimage"));
-	fprintf(stderr, "Updated preimage for '%s'\n", path);
+	fprintf_ln(stderr, _("Updated preimage for '%s'"), path);
 
 	/*
 	 * And remember that we can record resolution for this
@@ -1090,7 +1079,7 @@ static int rerere_forget_one_path(const char *path, struct string_list *rr)
 	item = string_list_insert(rr, path);
 	free_rerere_id(item);
 	item->util = id;
-	fprintf(stderr, "Forgot resolution for %s\n", path);
+	fprintf(stderr, _("Forgot resolution for '%s'\n"), path);
 	return 0;
 
 fail_exit:
@@ -1105,7 +1094,7 @@ int rerere_forget(struct pathspec *pathspec)
 	struct string_list merge_rr = STRING_LIST_INIT_DUP;
 
 	if (read_cache() < 0)
-		return error("Could not read index");
+		return error(_("index file corrupt"));
 
 	fd = setup_rerere(&merge_rr, RERERE_NOAUTOUPDATE);
 	if (fd < 0)
@@ -1193,7 +1182,7 @@ void rerere_gc(struct string_list *rr)
 	git_config(git_default_config, NULL);
 	dir = opendir(git_path("rr-cache"));
 	if (!dir)
-		die_errno("unable to open rr-cache directory");
+		die_errno(_("unable to open rr-cache directory"));
 	/* Collect stale conflict IDs ... */
 	while ((e = readdir(dir))) {
 		struct rerere_dir *rr_dir;

t/t4200-rerere.sh

@@ -577,4 +577,69 @@ test_expect_success 'multiple identical conflicts' '
 	count_pre_post 0 0
 '
 
+test_expect_success 'rerere with unexpected conflict markers does not crash' '
+	git reset --hard &&
+
+	git checkout -b branch-1 master &&
+	echo "bar" >test &&
+	git add test &&
+	git commit -q -m two &&
+
+	git reset --hard &&
+	git checkout -b branch-2 master &&
+	echo "foo" >test &&
+	git add test &&
+	git commit -q -a -m one &&
+
+	test_must_fail git merge branch-1 &&
+	echo "<<<<<<< a" >test &&
+	git rerere &&
+
+	git rerere clear
+'
+
+test_expect_success 'rerere with inner conflict markers' '
+	git reset --hard &&
+
+	git checkout -b A master &&
+	echo "bar" >test &&
+	git add test &&
+	git commit -q -m two &&
+	echo "baz" >test &&
+	git add test &&
+	git commit -q -m three &&
+
+	git reset --hard &&
+	git checkout -b B master &&
+	echo "foo" >test &&
+	git add test &&
+	git commit -q -a -m one &&
+
+	test_must_fail git merge A~ &&
+	git add test &&
+	git commit -q -m "will solve conflicts later" &&
+	test_must_fail git merge A &&
+
+	echo "resolved" >test &&
+	git add test &&
+	git commit -q -m "solved conflict" &&
+
+	echo "resolved" >expect &&
+
+	git reset --hard HEAD~~ &&
+	test_must_fail git merge A~ &&
+	git add test &&
+	git commit -q -m "will solve conflicts later" &&
+	test_must_fail git merge A &&
+	cat test >actual &&
+	test_cmp expect actual &&
+
+	git add test &&
+	git commit -m "rerere solved conflict" &&
+	git reset --hard HEAD~ &&
+	test_must_fail git merge A &&
+	cat test >actual &&
+	test_cmp expect actual
+'
+
 test_done