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Make the default abbrev length configurable

The default of 7 comes from fairly early in git development, when seven hex digits was a lot (it covers about 250+ million hash values). Back then I thought that 65k revisions was a lot (it was what we were about to hit in BK), and each revision tends to be about 5-10 new objects or so, so a million objects was a big number. These days, the kernel isn't even the largest git project, and even the kernel has about 220k revisions (_much_ bigger than the BK tree ever was) and we are approaching two million objects. At that point, seven hex digits is still unique for a lot of them, but when we're talking about just two orders of magnitude difference between number of objects and the hash size, there _will_ be collisions in truncated hash values. It's no longer even close to unrealistic - it happens all the time. We should both increase the default abbrev that was unrealistically small, _and_ add a way for people to set their own default per-project in the git config file. This is the first step to first make it configurable; the default of 7 is not raised yet. Signed-off-by: Junio C Hamano <gitster@pobox.com>

Linus Torvalds committed Oct 28, 2010 at 11:28 UTC dce96489162b05ae3463741f7f0365ff56f0de36

5 files changed +23 -3

Documentation/config.txt

@@ -567,6 +567,12 @@ core.sparseCheckout::

567 Enable "sparse checkout" feature. See section "Sparse checkout" in

568 linkgit:git-read-tree[1] for more information.

569

570 +core.abbrevLength::

571 + Set the length object names are abbreviated to. If unspecified,

572 + many commands abbreviate to 7 hexdigits, which may not be enough

573 + for abbreviated object names to stay unique for sufficiently long

574 + time.

575 +

576 add.ignore-errors::

577 add.ignoreErrors::

578 Tells 'git add' to continue adding files when some files cannot be

builtin/describe.c

+5 -1

@@ -21,7 +21,7 @@ static int debug; /* Display lots of verbose info */

21 static int all; /* Any valid ref can be used */

22 static int tags; /* Allow lightweight tags */

23 static int longformat;

24 -static int abbrev = DEFAULT_ABBREV;

24 +static int abbrev = -1; /* unspecified */

25 static int max_candidates = 10;

26 static struct hash_table names;

27 static int have_util;

@@ -420,7 +420,11 @@ int cmd_describe(int argc, const char **argv, const char *prefix)

420 OPT_END(),

421 };

422

423 + git_config(git_default_config, NULL);

424 argc = parse_options(argc, argv, prefix, options, describe_usage, 0);

425 + if (abbrev < 0)

426 + abbrev = DEFAULT_ABBREV;

427 +

428 if (max_candidates < 0)

429 max_candidates = 0;

430 else if (max_candidates > MAX_TAGS)

cache.h

+3 -2

@@ -540,6 +540,7 @@ extern int trust_executable_bit;

540 extern int trust_ctime;

541 extern int quote_path_fully;

542 extern int has_symlinks;

543 +extern int minimum_abbrev, default_abbrev;

544 extern int ignore_case;

545 extern int assume_unchanged;

546 extern int prefer_symlink_refs;

@@ -758,8 +759,8 @@ static inline unsigned int hexval(unsigned char c)

759 }

760

761 /* Convert to/from hex/sha1 representation */

761 -#define MINIMUM_ABBREV 4

762 -#define DEFAULT_ABBREV 7

762 +#define MINIMUM_ABBREV minimum_abbrev

763 +#define DEFAULT_ABBREV default_abbrev

764

765 struct object_context {

766 unsigned char tree[20];

config.c

@@ -531,6 +531,14 @@ static int git_default_core_config(const char *var, const char *value)

531 return 0;

532 }

533

534 + if (!strcmp(var, "core.abbrevlength")) {

535 + int abbrev = git_config_int(var, value);

536 + if (abbrev < minimum_abbrev || abbrev > 40)

537 + return -1;

538 + default_abbrev = abbrev;

539 + return 0;

540 + }

541 +

542 if (!strcmp(var, "core.loosecompression")) {

543 int level = git_config_int(var, value);

544 if (level == -1)

environment.c

@@ -15,6 +15,7 @@ int user_ident_explicitly_given;

15 int trust_executable_bit = 1;

16 int trust_ctime = 1;

17 int has_symlinks = 1;

18 +int minimum_abbrev = 4, default_abbrev = 7;

19 int ignore_case;

20 int assume_unchanged;

21 int prefer_symlink_refs;