Re: [PATCH 4/4] replace: add a --raw mode for --edit

2 messages, 2 authors, 2016-06-15 · open the first message on its own page

Re: [PATCH 4/4] replace: add a --raw mode for --edit

From: Junio C Hamano <hidden>
Date: 2016-06-15 23:01:44

Jeff King [off-list ref] writes:
One of the purposes of "git replace --edit" is to help a
user repair objects which are malformed or corrupted.
Usually we pretty-print trees with "ls-tree", which is much
easier to work with than the raw binary data.  However, some
forms of corruption break the tree-walker, in which case our
pretty-printing fails, rendering "--edit" useless for the
user.

This patch introduces a "--raw" option, which lets you edit
the binary data in these instances.

Signed-off-by: Jeff King <redacted>
---
Hmmmmm, this feels almost like inviting accidents to make it easy
and limiting the attempt to only one shot at the "transformation"
step.

Will queue, but we can do the same with "cat-file $type >temp", do
some transformation on "temp", doubly make sure what is in "temp" is
sensible and then finally "hash-object -w -t $type temp".  And it
makes me feel uneasy that the new feature seems to make it harder to
do the "doubly make sure" part.

I dunno.
quoted hunk
 Documentation/git-replace.txt |  8 ++++++++
 builtin/replace.c             | 31 +++++++++++++++++++++----------
 2 files changed, 29 insertions(+), 10 deletions(-)
diff --git a/Documentation/git-replace.txt b/Documentation/git-replace.txt
index 61461b9..089dcac 100644
--- a/Documentation/git-replace.txt
+++ b/Documentation/git-replace.txt
@@ -73,6 +73,14 @@ OPTIONS
 	newly created object. See linkgit:git-var[1] for details about
 	how the editor will be chosen.
 
+--raw::
+	When editing, provide the raw object contents rather than
+	pretty-printed ones. Currently this only affects trees, which
+	will be shown in their binary form. This is harder to work with,
+	but can help when repairing a tree that is so corrupted it
+	cannot be pretty-printed. Note that you may need to configure
+	your editor to cleanly read and write binary data.
+
 -l <pattern>::
 --list <pattern>::
 	List replace refs for objects that match the given pattern (or
diff --git a/builtin/replace.c b/builtin/replace.c
index 2584170..d1ea2c2 100644
--- a/builtin/replace.c
+++ b/builtin/replace.c
@@ -188,10 +188,12 @@ static int replace_object(const char *object_ref, const char *replace_ref, int f
 }
 
 /*
- * Write the contents of the object named by "sha1" to the file "filename",
- * pretty-printed for human editing based on its type.
+ * Write the contents of the object named by "sha1" to the file "filename".
+ * If "raw" is true, then the object's raw contents are printed according to
+ * "type". Otherwise, we pretty-print the contents for human editing.
  */
-static void export_object(const unsigned char *sha1, const char *filename)
+static void export_object(const unsigned char *sha1, enum object_type type,
+			  int raw, const char *filename)
 {
 	struct child_process cmd = { NULL };
 	int fd;
@@ -202,7 +204,10 @@ static void export_object(const unsigned char *sha1, const char *filename)
 
 	argv_array_push(&cmd.args, "--no-replace-objects");
 	argv_array_push(&cmd.args, "cat-file");
-	argv_array_push(&cmd.args, "-p");
+	if (raw)
+		argv_array_push(&cmd.args, typename(type));
+	else
+		argv_array_push(&cmd.args, "-p");
 	argv_array_push(&cmd.args, sha1_to_hex(sha1));
 	cmd.git_cmd = 1;
 	cmd.out = fd;
@@ -217,7 +222,7 @@ static void export_object(const unsigned char *sha1, const char *filename)
  * The sha1 of the written object is returned via sha1.
  */
 static void import_object(unsigned char *sha1, enum object_type type,
-			  const char *filename)
+			  int raw, const char *filename)
 {
 	int fd;
 
@@ -225,7 +230,7 @@ static void import_object(unsigned char *sha1, enum object_type type,
 	if (fd < 0)
 		die_errno("unable to open %s for reading", filename);
 
-	if (type == OBJ_TREE) {
+	if (!raw && type == OBJ_TREE) {
 		const char *argv[] = { "mktree", NULL };
 		struct child_process cmd = { argv };
 		struct strbuf result = STRBUF_INIT;
@@ -265,7 +270,7 @@ static void import_object(unsigned char *sha1, enum object_type type,
 	 */
 }
 
-static int edit_and_replace(const char *object_ref, int force)
+static int edit_and_replace(const char *object_ref, int force, int raw)
 {
 	char *tmpfile = git_pathdup("REPLACE_EDITOBJ");
 	enum object_type type;
@@ -281,10 +286,10 @@ static int edit_and_replace(const char *object_ref, int force)
 
 	check_ref_valid(old, prev, ref, sizeof(ref), force);
 
-	export_object(old, tmpfile);
+	export_object(old, type, raw, tmpfile);
 	if (launch_editor(tmpfile, NULL, NULL) < 0)
 		die("editing object file failed");
-	import_object(new, type, tmpfile);
+	import_object(new, type, raw, tmpfile);
 
 	free(tmpfile);
 
@@ -297,6 +302,7 @@ static int edit_and_replace(const char *object_ref, int force)
 int cmd_replace(int argc, const char **argv, const char *prefix)
 {
 	int force = 0;
+	int raw = 0;
 	const char *format = NULL;
 	enum {
 		MODE_UNSPECIFIED = 0,
@@ -310,6 +316,7 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 		OPT_CMDMODE('d', "delete", &cmdmode, N_("delete replace refs"), MODE_DELETE),
 		OPT_CMDMODE('e', "edit", &cmdmode, N_("edit existing object"), MODE_EDIT),
 		OPT_BOOL('f', "force", &force, N_("replace the ref if it exists")),
+		OPT_BOOL(0, "raw", &raw, N_("do not pretty-print contents for --edit")),
 		OPT_STRING(0, "format", &format, N_("format"), N_("use this format")),
 		OPT_END()
 	};
@@ -329,6 +336,10 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 		usage_msg_opt("-f only makes sense when writing a replacement",
 			      git_replace_usage, options);
 
+	if (raw && cmdmode != MODE_EDIT)
+		usage_msg_opt("--raw only makes sense with --edit",
+			      git_replace_usage, options);
+
 	switch (cmdmode) {
 	case MODE_DELETE:
 		if (argc < 1)
@@ -346,7 +357,7 @@ int cmd_replace(int argc, const char **argv, const char *prefix)
 		if (argc != 1)
 			usage_msg_opt("-e needs exactly one argument",
 				      git_replace_usage, options);
-		return edit_and_replace(argv[0], force);
+		return edit_and_replace(argv[0], force, raw);
 
 	case MODE_LIST:
 		if (argc > 1)

Re: [PATCH 4/4] replace: add a --raw mode for --edit

From: Jeff King <hidden>
Date: 2016-06-15 23:01:45

On Wed, Jun 25, 2014 at 03:33:42PM -0700, Junio C Hamano wrote:
Jeff King [off-list ref] writes:
quoted
One of the purposes of "git replace --edit" is to help a
user repair objects which are malformed or corrupted.
Usually we pretty-print trees with "ls-tree", which is much
easier to work with than the raw binary data.  However, some
forms of corruption break the tree-walker, in which case our
pretty-printing fails, rendering "--edit" useless for the
user.

This patch introduces a "--raw" option, which lets you edit
the binary data in these instances.

Signed-off-by: Jeff King <redacted>
---
Hmmmmm, this feels almost like inviting accidents to make it easy
and limiting the attempt to only one shot at the "transformation"
step.

Will queue, but we can do the same with "cat-file $type >temp", do
some transformation on "temp", doubly make sure what is in "temp" is
sensible and then finally "hash-object -w -t $type temp".  And it
makes me feel uneasy that the new feature seems to make it harder to
do the "doubly make sure" part.
I do not think it is any worse than "--edit" is by itself. True, editing
the binary contents is hard, but we do check that the format is sane
when we read it back in (using the same checks that hash-object does). I
think it would be nice to take that a step further and actually let
hash-object (and "replace --edit") do the more rigorous fsck checks on
created objects.

I do still think even with those automated sanity checks that it makes
sense to double-check the replacement manually. But I think that is one
of the features of replace objects: you are not doing anything
permanent, and can view the object in place. So not only can you examine
the object by "git show $new_sha1", you can see it in place as "git log
-p", etc. And easily back it out with "git replace -d" (or fix it up
again with "git replace --edit") if need be.

-Peff
Keyboard shortcuts
hback out one level
jnext message in thread
kprevious message in thread
ldrill in
Escclose help / fold thread tree
?toggle this help