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When prefetching the commit graph for the first time with `trust-pack-indexes=false`, the first pack file is the largest and takes the longest to index. In my test case, it takes ~2 minutes to fetch all the pack files, ~13 minutes to index the first pack file, and less than 1 minute to index the rest. A previous pull request parallelized the pack file indexing. This pull request makes it so as soon as the smaller, more recent pack files are ready they are moved into the live pack folder and can be accessed by the user's operations. A marker file is created when a pack file is moved into the live pack folder ahead of an older pack file still indexing. If the prefetch is interrupted, the next prefetch will ignore pack files which have the marker when determining the timestamp for the prefetch, which ensures that any missing pack files from the interrupted prefetch are redownloaded. The marker file is deleted once all the previous pack files are ready. After a completed prefetch, any markers (and the pack and index files they mark) left over from previous incomplete prefetches are deleted.
Make ready pack files available during prefetch
The previous implementation of GetHeadTreeId called "git show -s". "-s" suppresses the diff from the output, but it turns out git still performs the diff operation internally. The inefficiency isn't necessarily an issue, but we are running git.exe with the virtualization hook off so if the objects required for the diff are not already downloaded the command will fail. The new implementation produces the same output, but doesn't try to do a diff at all.
Fix GetHeadTreeId to only read head commit
tyrielv
approved these changes
Dec 16, 2025
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