On Tue, Sep 17, 2013 at 04:56:16PM -0400, Jeff King wrote:
> On Tue, Sep 17, 2013 at 11:38:07PM +0300, Michael S. Tsirkin wrote:
>
> > > A problem with both schemes, though, is that they are not
> > > backwards-compatible with existing git-patch-id implementations.
> >
> > Could you clarify?
> > We never send patch IDs on the wire - how isn't this compatible?
>
> I meant that you might be comparing patch-ids generated by different
> implementations, or across time. There are no dedicated tools to do so,
> but it is very easy to do so with standard tools like "join".
>
> For example, you can do:
>
> patch_ids() {
> git rev-list "$1" |
> git diff-tree --stdin -p |
> git patch-id |
> sort
> }
>
> patch_ids origin..topic1 >us
> patch_ids origin..topic2 >them
>
> join us them | cut -d' ' -f2-3
>
> to get a list of correlated commits between two branches. If the "them"
> was on another machine with a different implementation (or is saved from
> an earlier time), your patch-ids would not match.
>
> It may be esoteric enough not to worry about, though. By far the most
> common use of patch-ids is going to be in a single "rev-list
> --cherry-pick" situation where you are trying to omit commits during
> a rebase.
>
> I am mostly thinking of the problems we had with the "kup" tool, which
> expected stability across diffs that would be signed by both kernel.org.
> But as far as I know, they do not use patch-id. More details in case you
> are curious (including me arguing that we should not care, and it is
> kup's problem!) are here:
>
> http://thread.gmane.org/gmane.comp.version-control.git/192331/focus=192424
>
> rerere is mentioned in that thread, but I believe that it does its own
> hash, and does not rely on patch-id.
>
> -Peff
OK so far I came up with the following.
Needs documentation and tests obviously.
But besides that -
would something like this be enough to address the
issue Junio raised?
--->
patch-id: make it more stable
Add a new patch-id algorithm making it stable against
hunk reodering:
- prepend header to each hunk (if not there)
- calculate SHA1 hash for each hunk separately
- sum all hashes to get patch id
Add --order-sensitive to get historical unstable behaviour.
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
builtin/patch-id.c | 65 +++++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 50 insertions(+), 15 deletions(-)
diff --git a/builtin/patch-id.c b/builtin/patch-id.c
index 3cfe02d..d1902ff 100644
--- a/builtin/patch-id.c
+++ b/builtin/patch-id.c
@@ -1,17 +1,14 @@
#include "builtin.h"
-static void flush_current_id(int patchlen, unsigned char *id, git_SHA_CTX *c)
+static void flush_current_id(int patchlen, unsigned char *id, unsigned char *result)
{
- unsigned char result[20];
char name[50];
if (!patchlen)
return;
- git_SHA1_Final(result, c);
memcpy(name, sha1_to_hex(id), 41);
printf("%s %s\n", sha1_to_hex(result), name);
- git_SHA1_Init(c);
}
static int remove_space(char *line)
@@ -56,10 +53,30 @@ static int scan_hunk_header(const char *p, int *p_before, int *p_after)
return 1;
}
-static int get_one_patchid(unsigned char *next_sha1, git_SHA_CTX *ctx, struct strbuf *line_buf)
+static void flush_one_hunk(unsigned char *result, git_SHA_CTX *ctx)
{
- int patchlen = 0, found_next = 0;
+ unsigned char hash[20];
+ unsigned short carry = 0;
+ int i;
+
+ git_SHA1_Final(hash, ctx);
+ git_SHA1_Init(ctx);
+ /* 20-byte sum, with carry */
+ for (i = 0; i < 20; ++i) {
+ carry += result[i] + hash[i];
+ result[i] = carry;
+ carry >>= 8;
+ }
+}
+static int get_one_patchid(unsigned char *next_sha1, unsigned char *result,
+ struct strbuf *line_buf, int stable)
+{
+ int patchlen = 0, found_next = 0, hunks = 0;
int before = -1, after = -1;
+ git_SHA_CTX ctx, header_ctx;
+
+ git_SHA1_Init(&ctx);
+ hashclr(result);
while (strbuf_getwholeline(line_buf, stdin, '\n') != EOF) {
char *line = line_buf->buf;
@@ -99,6 +116,18 @@ static int get_one_patchid(unsigned char *next_sha1, git_SHA_CTX *ctx, struct st
if (!memcmp(line, "@@ -", 4)) {
/* Parse next hunk, but ignore line numbers. */
scan_hunk_header(line, &before, &after);
+ if (stable) {
+ if (hunks) {
+ flush_one_hunk(result, &ctx);
+ memcpy(&ctx, &header_ctx,
+ sizeof ctx);
+ } else {
+ /* Save ctx for next hunk. */
+ memcpy(&header_ctx, &ctx,
+ sizeof ctx);
+ }
+ }
+ hunks++;
continue;
}
@@ -108,6 +137,7 @@ static int get_one_patchid(unsigned char *next_sha1, git_SHA_CTX *ctx, struct st
/* Else we're parsing another header. */
before = after = -1;
+ hunks = 0;
}
/* If we get here, we're inside a hunk. */
@@ -119,27 +149,27 @@ static int get_one_patchid(unsigned char *next_sha1, git_SHA_CTX *ctx, struct st
/* Compute the sha without whitespace */
len = remove_space(line);
patchlen += len;
- git_SHA1_Update(ctx, line, len);
+ git_SHA1_Update(&ctx, line, len);
}
if (!found_next)
hashclr(next_sha1);
+ flush_one_hunk(result, &ctx);
+
return patchlen;
}
-static void generate_id_list(void)
+static void generate_id_list(int stable)
{
- unsigned char sha1[20], n[20];
- git_SHA_CTX ctx;
+ unsigned char sha1[20], n[20], result[20];
int patchlen;
struct strbuf line_buf = STRBUF_INIT;
- git_SHA1_Init(&ctx);
hashclr(sha1);
while (!feof(stdin)) {
- patchlen = get_one_patchid(n, &ctx, &line_buf);
- flush_current_id(patchlen, sha1, &ctx);
+ patchlen = get_one_patchid(n, result, &line_buf, stable);
+ flush_current_id(patchlen, sha1, result);
hashcpy(sha1, n);
}
strbuf_release(&line_buf);
@@ -149,9 +179,14 @@ static const char patch_id_usage[] = "git patch-id < patch";
int cmd_patch_id(int argc, const char **argv, const char *prefix)
{
- if (argc != 1)
+ int stable;
+ if (argc == 2 && !strcmp(argv[1], "--order-sensitive"))
+ stable = 0;
+ else if (argc == 1)
+ stable = 1;
+ else
usage(patch_id_usage);
- generate_id_list();
+ generate_id_list(stable);
return 0;
}
--
MST
--
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