summaryrefslogtreecommitdiff
path: root/Documentation/technical/commit-graph.txt
AgeCommit message (Collapse)AuthorFilesLines
2020-08-13docs: commit-graph: fix some whitespace in the diagramLibravatar Johannes Berg1-3/+3
In the merge diagram, some whitespace is missing which makes it a bit confusing, fix that. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-12-06Merge branch 'jk/lore-is-the-archive'Libravatar Junio C Hamano1-5/+5
Doc update for the mailing list archiving and nntp service. * jk/lore-is-the-archive: doc: replace public-inbox links with lore.kernel.org doc: recommend lore.kernel.org over public-inbox.org
2019-11-30doc: replace public-inbox links with lore.kernel.orgLibravatar Jeff King1-5/+5
Since we're now recommending lore.kernel.org (and because the public-inbox.org domain might eventually go away), let's update our internal references to use it, too. That future-proofs our references, and sets the example we want people to follow. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-11-07Documentation: fix a bunch of typos, both old and newLibravatar Elijah Newren1-6/+6
Reported-by: Jens Schleusener <Jens.Schleusener@fossies.org> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-06-19commit-graph: create options for split filesLibravatar Derrick Stolee1-3/+4
The split commit-graph feature is now fully implemented, but needs some more run-time configurability. Allow direct callers to 'git commit-graph write --split' to specify the values used in the merge strategy and the expire time. Update the documentation to specify these values. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-06-19commit-graph: expire commit-graph filesLibravatar Derrick Stolee1-0/+15
As we merge commit-graph files in a commit-graph chain, we should clean up the files that are no longer used. This change introduces an 'expiry_window' value to the context, which is always zero (for now). We then check the modified time of each graph-{hash}.graph file in the $OBJDIR/info/commit-graphs folder and unlink the files that are older than the expiry_window. Since this is always zero, this immediately clears all unused graph files. We will update the value to match a config setting in a future change. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-06-19commit-graph: allow cross-alternate chainsLibravatar Derrick Stolee1-0/+40
In an environment like a fork network, it is helpful to have a commit-graph chain that spans both the base repo and the fork repo. The fork is usually a small set of data on top of the large repo, but sometimes the fork is much larger. For example, git-for-windows/git has almost double the number of commits as git/git because it rebases its commits on every major version update. To allow cross-alternate commit-graph chains, we need a few pieces: 1. When looking for a graph-{hash}.graph file, check all alternates. 2. When merging commit-graph chains, do not merge across alternates. 3. When writing a new commit-graph chain based on a commit-graph file in another object directory, do not allow success if the base file has of the name "commit-graph" instead of "commit-graphs/graph-{hash}.graph". Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-06-19commit-graph: merge commit-graph chainsLibravatar Derrick Stolee1-0/+80
When searching for a commit in a commit-graph chain of G graphs with N commits, the search takes O(G log N) time. If we always add a new tip graph with every write, the linear G term will start to dominate and slow the lookup process. To keep lookups fast, but also keep most incremental writes fast, create a strategy for merging levels of the commit-graph chain. The strategy is detailed in the commit-graph design document, but is summarized by these two conditions: 1. If the number of commits we are adding is more than half the number of commits in the graph below, then merge with that graph. 2. If we are writing more than 64,000 commits into a single graph, then merge with all lower graphs. The numeric values in the conditions above are currently constant, but can become config options in a future update. As we merge levels of the commit-graph chain, check that the commits still exist in the repository. A garbage-collection operation may have removed those commits from the object store and we do not want to persist them in the commit-graph chain. This is a non-issue if the 'git gc' process wrote a new, single-level commit-graph file. After we merge levels, the old graph-{hash}.graph files are no longer referenced by the commit-graph-chain file. We will expire these files in a future change. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-06-19commit-graph: document commit-graph chainsLibravatar Derrick Stolee1-0/+59
Add a basic description of commit-graph chains. More details about the feature will be added as we add functionality. This introduction gives a high-level overview to the goals of the feature and the basic layout of commit-graph chains. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-06-12commit-graph: remove Future Work sectionLibravatar Derrick Stolee1-17/+0
The commit-graph feature began with a long list of planned benefits, most of which are now complete. The future work section has only a few items left. As for making more algorithms aware of generation numbers, some are only waiting for generation number v2 to ensure the performance matches the existing behavior using commit date. It is unlikely that we will ever send a commit-graph file as part of the protocol, since we would need to verify the data, and that is expensive. If we want to start trusting remote content, then that item can be investigated again. While there is more work to be done on the feature, having a section of the docs devoted to a TODO list is wasteful and hard to keep up-to-date. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-10-16Merge branch 'ma/commit-graph-docs'Libravatar Junio C Hamano1-4/+4
Doc update. * ma/commit-graph-docs: Doc: refer to the "commit-graph file" with dash git-commit-graph.txt: refer to "*commit*-graph file" git-commit-graph.txt: typeset more in monospace git-commit-graph.txt: fix bullet lists
2018-09-27Doc: refer to the "commit-graph file" with dashLibravatar Martin Ågren1-4/+4
The file processed by `git commit-graph` is referred to as the "commit-graph file", also with a dash. We have a few references to the "commit graph file", though, without the dash. These occur in git-commit-graph.txt as well as in Doc/technical/commit-graph.txt. Fix them. Do not change the references to the "commit graph" (without "... file") as a data structure. Signed-off-by: Martin Ågren <martin.agren@gmail.com> Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-08-21commit-graph: update design documentLibravatar Derrick Stolee1-3/+15
As it exists right now, the commit-graph feature may provide inconsistent results when combined with commit grafts, replace objects, and shallow clones. Update the design document to discuss why these interactions are difficult to reconcile and how we will avoid errors by preventing updates to and reads from the commit-graph file when these other features exist. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-06-27commit-graph: update design documentLibravatar Derrick Stolee1-22/+0
The commit-graph feature is now integrated with 'fsck' and 'gc', so remove those items from the "Future Work" section of the commit-graph design document. Also remove the section on lazy-loading trees, as that was completed in an earlier patch series. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-05-22commit-graph.txt: update design documentLibravatar Derrick Stolee1-5/+24
We now calculate generation numbers in the commit-graph file and use them in paint_down_to_common(). Expand the section on generation numbers to discuss how the three special generation numbers GENERATION_NUMBER_INFINITY, _ZERO, and _MAX interact with other generation numbers. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-04-02graph: add commit graph design documentLibravatar Derrick Stolee1-0/+163
Add Documentation/technical/commit-graph.txt with details of the planned commit graph feature, including future plans. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>