The `git sparse-checkout` command is available only since Git version
v2.25.0. The `actions/checkout` Action actually supports older Git
versions than that; As of time of writing, the minimum version is
v2.18.0.
Instead of raising this minimum version even for users who do not
require a sparse checkout, only check for this minimum version
specifically when a sparse checkout was asked for.
Suggested-by: Tingluo Huang <tingluohuang@github.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
When trying to list local branches to figure out what needs cleaned up during runs on non-ephemeral Actions Runners, we use git rev-parse --symbolic-full-name to get a list of branches. This can lead to ambiguous ref name errors when there are branches and tags with similar names.
Part of the reason we use rev-parse --symbolic-full-name vs git branch --list or git rev-parse --symbolic seems to related to a bug in Git 2.18. Until we can deprecate our usage of Git 2.18, I think we need to keep --symbolic-full-name. Since part of the problem is that these ambiguous ref name errors clog the Actions annotation limits, this is a mitigation to suppress those messages until we can get rid of the workaround.
