Re: [PATCH 1/2] sha1_name.c: signal if @{-N} was a true branch nameor a detached head

On Wed, May 8, 2013 at 5:12 PM, Junio C Hamano [off-list ref] wrote:

sha1_name.c: signal if @{-N} was a true branch nameor a detached head

s/nameor/name or/

The original API read "checkout: moving from (.*) to ..." from the
reflog of the HEAD, and returned the substring between "from" and
"to", but there was no way, if the substring was a 40-hex string, to
tell if we were on a detached HEAD at that commit object, or on a
branch whose name happened to be the 40-hex string.

At this point, we cannot afford to change the format recorded in the
reflog, so introduce a heuristics to see if the 40-hex matches the
object name of the commit we are switching out of.  This will
unfortunately mishandle this case:

        HEX=$(git rev-parse master)
        git checkout -b $HEX master
        git checkout master

where we were indeed on a non-detached $HEX branch (i.e. HEAD was
pointing at refs/heads/$HEX, not storing $HEX), of course, but
otherwise should be fairly reliable.

Signed-off-by: Junio C Hamano <redacted>