diff options
| -rw-r--r-- | Documentation/git-patch-id.txt | 37 | ||||
| -rw-r--r-- | builtin/patch-id.c | 74 |
2 files changed, 91 insertions, 20 deletions
diff --git a/Documentation/git-patch-id.txt b/Documentation/git-patch-id.txt index 312c3b1fe5..31efc587ee 100644 --- a/Documentation/git-patch-id.txt +++ b/Documentation/git-patch-id.txt @@ -8,14 +8,14 @@ git-patch-id - Compute unique ID for a patch SYNOPSIS -------- [verse] -'git patch-id' < <patch> +'git patch-id' [--stable | --unstable] < <patch> DESCRIPTION ----------- -A "patch ID" is nothing but a SHA-1 of the diff associated with a patch, with -whitespace and line numbers ignored. As such, it's "reasonably stable", but at -the same time also reasonably unique, i.e., two patches that have the same "patch -ID" are almost guaranteed to be the same thing. +A "patch ID" is nothing but a sum of SHA-1 of the file diffs associated with a +patch, with whitespace and line numbers ignored. As such, it's "reasonably +stable", but at the same time also reasonably unique, i.e., two patches that +have the same "patch ID" are almost guaranteed to be the same thing. IOW, you can use this thing to look for likely duplicate commits. @@ -27,6 +27,33 @@ This can be used to make a mapping from patch ID to commit ID. OPTIONS ------- + +--stable:: + Use a "stable" sum of hashes as the patch ID. With this option: + - Reordering file diffs that make up a patch does not affect the ID. + In particular, two patches produced by comparing the same two trees + with two different settings for "-O<orderfile>" result in the same + patch ID signature, thereby allowing the computed result to be used + as a key to index some meta-information about the change between + the two trees; + + - Result is different from the value produced by git 1.9 and older + or produced when an "unstable" hash (see --unstable below) is + configured - even when used on a diff output taken without any use + of "-O<orderfile>", thereby making existing databases storing such + "unstable" or historical patch-ids unusable. + + This is the default if patchid.stable is set to true. + +--unstable:: + Use an "unstable" hash as the patch ID. With this option, + the result produced is compatible with the patch-id value produced + by git 1.9 and older. Users with pre-existing databases storing + patch-ids produced by git 1.9 and older (who do not deal with reordered + patches) may want to use this option. + + This is the default. + <patch>:: The diff to create the ID of. diff --git a/builtin/patch-id.c b/builtin/patch-id.c index 3cfe02d5a5..77db8739b5 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 +53,31 @@ 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) +{ + 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; int before = -1, after = -1; + git_SHA_CTX ctx; + + git_SHA1_Init(&ctx); + hashclr(result); while (strbuf_getwholeline(line_buf, stdin, '\n') != EOF) { char *line = line_buf->buf; @@ -107,6 +125,8 @@ static int get_one_patchid(unsigned char *next_sha1, git_SHA_CTX *ctx, struct st break; /* Else we're parsing another header. */ + if (stable) + flush_one_hunk(result, &ctx); before = after = -1; } @@ -119,39 +139,63 @@ 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); } -static const char patch_id_usage[] = "git patch-id < patch"; +static const char patch_id_usage[] = "git patch-id [--stable | --unstable] < patch"; + +static int git_patch_id_config(const char *var, const char *value, void *cb) +{ + int *stable = cb; + + if (!strcmp(var, "patchid.stable")) { + *stable = git_config_bool(var, value); + return 0; + } + + return git_default_config(var, value, cb); +} int cmd_patch_id(int argc, const char **argv, const char *prefix) { - if (argc != 1) + int stable = -1; + + git_config(git_patch_id_config, &stable); + + /* If nothing is set, default to unstable. */ + if (stable < 0) + stable = 0; + + if (argc == 2 && !strcmp(argv[1], "--stable")) + stable = 1; + else if (argc == 2 && !strcmp(argv[1], "--unstable")) + stable = 0; + else if (argc != 1) usage(patch_id_usage); - generate_id_list(); + generate_id_list(stable); return 0; } |