Add a quiet input to suppress git output

[mostafazh]

Adds a quiet input (default false) that passes --quiet to the git commands checkout runs: fetch, checkout, checkout --detach, and submodule update.

Fixes #2409.

Why show-progress: false is not enough

#1067 made --progress conditional, which handles the progress sideband. The noise reported in #2409 is a different thing: the per-ref fetch summary. At fetch-depth: 0 the refspec is +refs/heads/*:refs/remotes/origin/* plus +refs/tags/*:refs/tags/*, so git prints a From <url> line and then one * [new branch] / * [new tag] line for every ref in the repository. That output is not progress, so no --progress toggle removes it. --quiet does.

Evidence

Three jobs on the same runner, all fetching the same repository (actions/checkout, 61 branches + 68 tags) at fetch-depth: 0. The middle arm is a control — this branch with quiet: false — to show the change is inert unless the input is set.

Arm	Fetching the repository group	* [new ...] lines	Whole checkout step
stock actions/checkout@v7	135 lines	131	216 lines
this branch, quiet: false	135 lines	131	217 lines
this branch, quiet: true	3 lines	0	83 lines

The control arm's fetch group is content-identical to the baseline (0 differing lines once timestamps are stripped), so quiet is the only variable.

Baseline:

##[group]Fetching the repository
[command]/usr/bin/git -c protocol.version=2 fetch --no-tags --prune --no-recurse-submodules origin +refs/heads/*:refs/remotes/origin/* +refs/tags/*:refs/tags/*
From https://github.com/actions/checkout
 * [new branch]      Update-description      -> origin/Update-description
 * [new branch]      copilot/backport-2518-releases-v2 -> origin/copilot/backport-2518-releases-v2
 ... 129 more [new branch] / [new tag] lines ...
##[endgroup]

With quiet: true:

##[group]Fetching the repository
[command]/usr/bin/git -c protocol.version=2 fetch --no-tags --prune --no-recurse-submodules --quiet origin +refs/heads/*:refs/remotes/origin/* +refs/tags/*:refs/tags/*
##[endgroup]

Full run: https://github.com/mostafazh/checkout/actions/runs/33961567354 — workflow: https://github.com/mostafazh/checkout/blob/quiet-ab-test/.github/workflows/quiet-ab-test.yml

--progress vs --quiet

These two drive different output channels and compose rather than conflict, so this PR passes both where both apply:

• --progress / --no-progress controls only the progress meter (Receiving objects, Updating files: N%).
• -q / --quiet controls verbosity: the From <url> + * [new ...] ref summary for fetch, Switched to branch ... for checkout. It also turns the meter off as a side effect.

When both are given, the meter follows --progress (git evaluates forced progress before verbosity, and git-checkout(1) says --progress applies "regardless of --quiet"), while everything else stays suppressed by --quiet. Measured on git 2.50.1 over file:// with stderr not a terminal:

git fetch flags	progress lines	ref-summary lines
(none)	0	11
--progress	3	11
--quiet	0	0
--quiet --progress	3	0
--progress --quiet	3	0

Order is irrelevant; each flag acts on its own channel. So checkout keeps its unconditional --progress and merely gains --quiet, which means a large checkout still reports progress while the chatter goes away.

Separate observation, not fixed here

While tracing this I noticed show-progress currently has no effect. getSource declares showProgress?: boolean on the fetchOptions object in src/git-source-provider.ts but never assigns settings.showProgress to it, so options.showProgress is always undefined and --progress is never passed to fetch. This is visible in the baseline log above: the step's resolved inputs report show-progress: true, yet the fetch command carries no --progress. It appears to date back to #1067, which added the field to the type but not the assignment.

I have deliberately left it alone to keep this PR focused, and because wiring it up would make the default output noisier for everyone. Happy to open a separate issue or PR if you would like it addressed.

Notes

• git lfs fetch has no --quiet flag, so LFS output is unchanged.
• The default is false, so existing workflows are unaffected.

Per CONTRIBUTING

• Tests added. __test__/git-command-manager.test.ts gains a Test quiet option block (11 cases) asserting the exact argv for fetch, checkout with and without a start point, checkoutDetach and submoduleUpdate in both the quiet and non-quiet states, plus --quiet taking precedence over --progress and the omitted-argument default staying non-quiet. __test__/input-helper.test.ts covers the input default and parsing.
• npm run test — 140 passing
• npm run format — clean
• npm run build — dist/index.js rebuilt and committed

[mostafazh]

Before and After Logs: https://github.com/proxy/gist.github.com/mostafazh/7badb07f545eb6d1913c382962b346cc (48% less in Number of Lines)

[mostafazh]

@aiqiaoy @yaananth can you please review? 🙏

[mostafazh]

@aiqiaoy @yaananth can you please review? 🙏