| commit | c1a09119f68d9800be53f544389f9ef83258ee7f | [log] [tgz] |
|---|---|---|
| author | Abhishek Kumar <abhishekkumar8222@gmail.com> | Sat Jan 16 18:11:14 2021 +0000 |
| committer | Junio C Hamano <gitster@pobox.com> | Mon Jan 18 16:21:18 2021 -0800 |
| tree | 28b01d46948bd976e1e0b4d3d7d38772925695f7 | |
| parent | d7f92784c65b143c5ec9f435484146b6098c2f85 [diff] |
commit-graph: implement corrected commit date With most of preparations done, let's implement corrected commit date. The corrected commit date for a commit is defined as: * A commit with no parents (a root commit) has corrected commit date equal to its committer date. * A commit with at least one parent has corrected commit date equal to the maximum of its commit date and one more than the largest corrected commit date among its parents. As a special case, a root commit with timestamp of zero (01.01.1970 00:00:00Z) has corrected commit date of one, to be able to distinguish from GENERATION_NUMBER_ZERO (that is, an uncomputed corrected commit date). To minimize the space required to store corrected commit date, Git stores corrected commit date offsets into the commit-graph file. The corrected commit date offset for a commit is defined as the difference between its corrected commit date and actual commit date. Storing corrected commit date requires sizeof(timestamp_t) bytes, which in most cases is 64 bits (uintmax_t). However, corrected commit date offsets can be safely stored using only 32-bits. This halves the size of GDAT chunk, which is a reduction of around 6% in the size of commit-graph file. However, using offsets be problematic if a commit is malformed but valid and has committer date of 0 Unix time, as the offset would be the same as corrected commit date and thus require 64-bits to be stored properly. While Git does not write out offsets at this stage, Git stores the corrected commit dates in member generation of struct commit_graph_data. It will begin writing commit date offsets with the introduction of generation data chunk. Signed-off-by: Abhishek Kumar <abhishekkumar8222@gmail.com> Reviewed-by: Taylor Blau <me@ttaylorr.com> Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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