delta/git.git, branch ds/commit-graph

SQUASH??? sparse fixes

2018-03-14T21:44:38+00:00

commit-graph: implement "--additive" option

2018-03-14T21:01:36+00:00

Teach git-commit-graph to add all commits from the existing
commit-graph file to the file about to be written. This should be
used when adding new commits without performing garbage collection.

Signed-off-by: Derrick Stolee 
Signed-off-by: Junio C Hamano

commit-graph: build graph from starting commits

2018-03-14T21:01:27+00:00

Teach git-commit-graph to read commits from stdin when the
--stdin-commits flag is specified. Commits reachable from these
commits are added to the graph. This is a much faster way to construct
the graph than inspecting all packed objects, but is restricted to
known tips.

For the Linux repository, 700,000+ commits were added to the graph
file starting from 'master' in 7-9 seconds, depending on the number
of packfiles in the repo (1, 24, or 120).

Signed-off-by: Derrick Stolee 
Signed-off-by: Junio C Hamano

commit-graph: read only from specific pack-indexes

2018-03-14T20:58:15+00:00

Teach git-commit-graph to inspect the objects only in a certain list
of pack-indexes within the given pack directory. This allows updating
the commit graph iteratively.

Signed-off-by: Derrick Stolee 
Signed-off-by: Junio C Hamano

commit: integrate commit graph with commit parsing

2018-03-14T20:58:14+00:00

Teach Git to inspect a commit graph file to supply the contents of a
struct commit when calling parse_commit_gently(). This implementation
satisfies all post-conditions on the struct commit, including loading
parents, the root tree, and the commit date.

If core.commitGraph is false, then do not check graph files.

In test script t5318-commit-graph.sh, add output-matching conditions on
read-only graph operations.

By loading commits from the graph instead of parsing commit buffers, we
save a lot of time on long commit walks. Here are some performance
results for a copy of the Linux repository where 'master' has 678,653
reachable commits and is behind 'origin/master' by 59,929 commits.

| Command                          | Before | After  | Rel % |
|----------------------------------|--------|--------|-------|
| log --oneline --topo-order -1000 |  8.31s |  0.94s | -88%  |
| branch -vv                       |  1.02s |  0.14s | -86%  |
| rev-list --all                   |  5.89s |  1.07s | -81%  |
| rev-list --all --objects         | 66.15s | 58.45s | -11%  |

Signed-off-by: Derrick Stolee 
Signed-off-by: Junio C Hamano

commit-graph: close under reachability

2018-03-14T20:58:14+00:00

Teach write_commit_graph() to walk all parents from the commits
discovered in packfiles. This prevents gaps given by loose objects or
previously-missed packfiles.

Also automatically add commits from the existing graph file, if it
exists.

Signed-off-by: Derrick Stolee 
Signed-off-by: Junio C Hamano

commit-graph: add core.commitGraph setting

2018-03-14T20:58:14+00:00

The commit graph feature is controlled by the new core.commitGraph config
setting. This defaults to 0, so the feature is opt-in.

The intention of core.commitGraph is that a user can always stop checking
for or parsing commit graph files if core.commitGraph=0.

Signed-off-by: Derrick Stolee 
Signed-off-by: Junio C Hamano

commit-graph: implement git commit-graph read

2018-03-14T20:58:14+00:00

Teach git-commit-graph to read commit graph files and summarize their contents.

Use the read subcommand to verify the contents of a commit graph file in the
tests.

Signed-off-by: Derrick Stolee 
Signed-off-by: Junio C Hamano

commit-graph: implement 'git-commit-graph write'

2018-03-14T20:58:14+00:00

Teach git-commit-graph to write graph files. Create new test script to verify
this command succeeds without failure.

Signed-off-by: Derrick Stolee 
Signed-off-by: Junio C Hamano

commit-graph: implement write_commit_graph()

2018-03-14T20:58:14+00:00

Teach Git to write a commit graph file by checking all packed objects
to see if they are commits, then store the file in the given object
directory.

Signed-off-by: Derrick Stolee 
Signed-off-by: Junio C Hamano