Re: [PATCH 2/2] reflog: ignore expire-unreachable for "HEAD" reflog

> "git reflog expire" (and "git gc") examines the reflog entries and
> discards old/stale ones using two criteria.  The entries that are older
> than "reflogexpire" (defaults to 90 days) are unconditionally removed, and
> the entries that are older than "reflogexpireunreachable" (defaults to 30
> days) are removed if the entry point at commits that are not reachable
> from the value of the ref.
> 
> This is reasonable for local branches, remote tracking branches and tags.
> You (or other people) may have failed experiments that have been made and
> then later discarded by resetting the tip of the branch back, and setting
> the value of "reflogexpireunreachable" shorter than that of "reflogexpire"
> will prune the entries that describe these failed experiments earlier than
> the entries that describe the steps that led to the current history.
> 
> It however doesn't make much sense for "HEAD" reflog.  When you switch
> between branches, it is normal that the tip of the branch you were on is
> not an ancestor of the branch you have switched to.  Expiring the entries
> that describe what you did while on the previous branch earlier than usual
> does not help.