From 65acfeacaa6e50c92a6ac18dc08356026a99b3f3 Mon Sep 17 00:00:00 2001 From: Junio C Hamano Date: Fri, 30 Sep 2016 17:19:35 -0700 Subject: abbrev: add FALLBACK_DEFAULT_ABBREV to prepare for auto sizing We'll be introducing a new way to decide the default abbreviation length by initialising DEFAULT_ABBREV to -1 to signal the first call to "find unique abbreviation" codepath to compute a reasonable value based on the number of objects we have to avoid collisions. We have long relied on DEFAULT_ABBREV being a positive concrete value that is used as the abbreviation length when no extra configuration or command line option has overridden it. Some codepaths wants to use such a positive concrete default value even before making their first request to actually trigger the computation for the auto sized default. Introduce FALLBACK_DEFAULT_ABBREV and use it to the code that attempts to align the report from "git fetch". For now, this macro is also used to initialize the default_abbrev variable, but the auto-sizing code will use -1 and then use the value of FALLBACK_DEFAULT_ABBREV as the starting point of auto-sizing. Signed-off-by: Junio C Hamano --- environment.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'environment.c') diff --git a/environment.c b/environment.c index cd5aa57179..44fb107b8a 100644 --- a/environment.c +++ b/environment.c @@ -16,7 +16,7 @@ int trust_executable_bit = 1; int trust_ctime = 1; int check_stat = 1; int has_symlinks = 1; -int minimum_abbrev = 4, default_abbrev = 7; +int minimum_abbrev = 4, default_abbrev = FALLBACK_DEFAULT_ABBREV; int ignore_case; int assume_unchanged; int prefer_symlink_refs; -- cgit v1.2.1 From e6c587c733b4634030b353f4024794b08bc86892 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 30 Sep 2016 17:19:37 -0700 Subject: abbrev: auto size the default abbreviation In fairly early days we somehow decided to abbreviate object names down to 7-hexdigits, but as projects grow, it is becoming more and more likely to see such a short object names made in earlier days and recorded in the log messages no longer unique. Currently the Linux kernel project needs 11 to 12 hexdigits, while Git itself needs 10 hexdigits to uniquely identify the objects they have, while many smaller projects may still be fine with the original 7-hexdigit default. One-size does not fit all projects. Introduce a mechanism, where we estimate the number of objects in the repository upon the first request to abbreviate an object name with the default setting and come up with a sane default for the repository. Based on the expectation that we would see collision in a repository with 2^(2N) objects when using object names shortened to first N bits, use sufficient number of hexdigits to cover the number of objects in the repository. Each hexdigit (4-bits) we add to the shortened name allows us to have four times (2-bits) as many objects in the repository. Signed-off-by: Linus Torvalds Signed-off-by: Junio C Hamano --- environment.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'environment.c') diff --git a/environment.c b/environment.c index 44fb107b8a..6f9d290563 100644 --- a/environment.c +++ b/environment.c @@ -16,7 +16,7 @@ int trust_executable_bit = 1; int trust_ctime = 1; int check_stat = 1; int has_symlinks = 1; -int minimum_abbrev = 4, default_abbrev = FALLBACK_DEFAULT_ABBREV; +int minimum_abbrev = 4, default_abbrev = -1; int ignore_case; int assume_unchanged; int prefer_symlink_refs; -- cgit v1.2.1