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reflog [git]

A reflog (= reference log) logs changes to references such as the tips of branches etc.

They're needed to specify old values of a reference (e.g. HEAD@{10}, master@{one.week.ago} etc., compar with gitrevisions).

Reflogs are found under .git/logs:

.git/logs/HEAD stores the history of HEAD values
.git/logs/refs stores the history of all refs, including the ref stash.
logs/refs/heads/some-branch-name stores the history of the head of some-branch-name

Enabling the reflog

The reflog is enabled by setting the option core.logAllRefUpdates.

The information stays in the reflogs until they expire.

By default, that is 30 days for unreachable commits and 90 days for reachable commits.

The default can be overwritten with the config options gc.reflogExpireUnreachable and gc.reflogExpire, respectively.