Jeff King <peff@xxxxxxxx> writes:
> On Thu, May 02, 2013 at 02:34:01AM +0530, Ramkumar Ramachandra wrote:
>
>> Junio C Hamano wrote:
>> > Just making sure. HEAD@{$n} and @{$n} for non-negative $n mean
>> > totally different things. @{0} and HEAD@{0} are almost always the
>> > same, and @{1} and HEAD@{1} may often happen to be the same, but as
>> > a blanket statement, I find "Since HEAD is implicit in @{}" very
>> > misleading.
>>
>> When will they be different? I'm looking at this from the parser's
>> point of view: when the part before @{} is missing, we dwim a "HEAD".
>
> The difference is that HEAD@{} refers to HEAD's reflog, but @{} refers
> to the reflog of the branch pointed to by HEAD. For example, try:
>
> git init repo && cd repo
> git commit --allow-empty -m one &&
> git commit --allow-empty -m two &&
> git checkout HEAD^ &&
> git commit --allow-empty -m three &&
> git checkout master &&
> for i in 0 1 2; do
> echo "HEAD@{$i}: $(git log -1 --oneline HEAD@{$i} 2>&1)"
> echo " @{$i}: $(git log -1 --oneline @{$i} 2>&1)"
> done
>
> which produces:
>
> HEAD@{0}: 1fbb097 two
> @{0}: 1fbb097 two
> HEAD@{1}: 42f3f4d three
> @{1}: 1089d0e one
> HEAD@{2}: 1089d0e one
> @{2}: fatal: Log for '' only has 2 entries.
>
> Unless your reflogs are screwed up, the 0th reflog should always point
> to the same commit (since you just moved HEAD there), but beyond that
> there is not necessarily any relation. And even for the 0th reflog
> entry, the reflog information is not the same. Try this on the repo
> above:
>
> echo "HEAD@{0}: $(git log -g -1 --format='%gd %gs' HEAD@{0})"
> echo " @{0}: $(git log -g -1 --format='%gd %gs' @{0})"
>
> which yields:
>
> HEAD@{0}: HEAD@{0} checkout: moving from ... to master
> @{0}: master@{0} commit: two
>
> -Peff
Thanks for helping with a basic education I found no time for
myself today.
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