[petertriho]

Summary

On line 1 of a commit message, cmp-git now completes the subjects that git rebase --autosquash reads.

• Prefix words: fi, sq, and am give fixup!, squash!, and amend!. git.autosquash.prefixes sets the words and the minimum number of letters (default 2). After a prefix item, the menu opens again with the commit titles.
• Commit titles: after fixup!, squash!, and amend!, the menu shows the commit titles, newest first, one item for each title. Titles that start with an autosquash prefix are hidden. The list uses the commit cache, so a cached history starts no new git process. A :, #, @, or ! in the title starts no other completion.
• The completion works only on line 1, in the filetypes of git.autosquash.filetypes (gitcommit and NeogitCommitMessage).
• Core loads only the line checks. Only the git source loads the autosquash capability.
• README.md and docs/configuration.md describe the feature, the config, and how to turn off each part.

Engine API used for the menu reopen

• nvim-cmp 2ffe79f: source.execute(self, item, callback) calls self.source:execute(item, callback) after the insert. cmp-git calls callback, then cmp.complete() with only the git source.
• blink.cmp v1.10.0-258-geece1c5: module:execute(context, item, resolve, default_implementation). cmp-git calls default_implementation and resolve, then blink.show() with the provider of the item.

Test plan

• make ci (StyLua, Selene, lua-language-server, 314 tests, 0 fails)
• make test in the nvim-0_12_0 shell (v0.12.0) and the nightly shell (v0.13.0-nightly+1cfebe9)
• A test runs git rebase -i --autosquash on completed subjects. Each commit comes right after its target with fixup, squash, or fixup -C.
• make bench-compare: no regression in the keystroke/ group
• Real Neovim 0.12.6, keys typed one at a time: blink.cmp passes 18 of 18 checks, nvim-cmp passes 16 of 18

Known limits

• nvim-cmp, f with min_length = 1: no item until the second letter. nvim-cmp starts no request for the first character typed after insert mode starts, for any source.
• nvim-cmp, squash! fixup! x: no item shows. cmp-git gives the titles with the edit after squash! , but nvim-cmp filters them on fixup! x, and no title matches. blink.cmp filters on the last word, so it shows the list.
• Startup benchmarks: require/setup allocates about 23 KB more (+12%), and new_source about 2.8 KB more. new_source_with_overrides allocates about 2.6 KB more and takes 26% longer. Setup loads the new code, copies the larger defaults, and compiles two more regexes.

Fixes #42