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>
This commit is contained in:
Linus Torvalds 2010-10-28 11:28:04 -07:00 committed by Junio C Hamano
parent 7ed863a85a
commit dce9648916
5 changed files with 23 additions and 3 deletions

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@ -567,6 +567,12 @@ core.sparseCheckout::
Enable "sparse checkout" feature. See section "Sparse checkout" in
linkgit:git-read-tree[1] for more information.
core.abbrevLength::
Set the length object names are abbreviated to. If unspecified,
many commands abbreviate to 7 hexdigits, which may not be enough
for abbreviated object names to stay unique for sufficiently long
time.
add.ignore-errors::
add.ignoreErrors::
Tells 'git add' to continue adding files when some files cannot be

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@ -21,7 +21,7 @@ static int debug; /* Display lots of verbose info */
static int all; /* Any valid ref can be used */
static int tags; /* Allow lightweight tags */
static int longformat;
static int abbrev = DEFAULT_ABBREV;
static int abbrev = -1; /* unspecified */
static int max_candidates = 10;
static struct hash_table names;
static int have_util;
@ -420,7 +420,11 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
OPT_END(),
};
git_config(git_default_config, NULL);
argc = parse_options(argc, argv, prefix, options, describe_usage, 0);
if (abbrev < 0)
abbrev = DEFAULT_ABBREV;
if (max_candidates < 0)
max_candidates = 0;
else if (max_candidates > MAX_TAGS)

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@ -540,6 +540,7 @@ extern int trust_executable_bit;
extern int trust_ctime;
extern int quote_path_fully;
extern int has_symlinks;
extern int minimum_abbrev, default_abbrev;
extern int ignore_case;
extern int assume_unchanged;
extern int prefer_symlink_refs;
@ -758,8 +759,8 @@ static inline unsigned int hexval(unsigned char c)
}
/* Convert to/from hex/sha1 representation */
#define MINIMUM_ABBREV 4
#define DEFAULT_ABBREV 7
#define MINIMUM_ABBREV minimum_abbrev
#define DEFAULT_ABBREV default_abbrev
struct object_context {
unsigned char tree[20];

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@ -531,6 +531,14 @@ static int git_default_core_config(const char *var, const char *value)
return 0;
}
if (!strcmp(var, "core.abbrevlength")) {
int abbrev = git_config_int(var, value);
if (abbrev < minimum_abbrev || abbrev > 40)
return -1;
default_abbrev = abbrev;
return 0;
}
if (!strcmp(var, "core.loosecompression")) {
int level = git_config_int(var, value);
if (level == -1)

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@ -15,6 +15,7 @@ int user_ident_explicitly_given;
int trust_executable_bit = 1;
int trust_ctime = 1;
int has_symlinks = 1;
int minimum_abbrev = 4, default_abbrev = 7;
int ignore_case;
int assume_unchanged;
int prefer_symlink_refs;