On Mon, Dec 03, 2018 at 02:30:44PM -0800, Matthew DeVore wrote:
> Here is a one-liner to do it. It is Perl line noise, so it's not very cute,
> thought that is subjective. The output shown below is for the Git project
> (not Linux) repository as I've currently synced it:
>
> $ git rev-list --objects HEAD | sort | perl -anE 'BEGIN { $prev = ""; $long
> = "" } $n = $F[0]; for my $i (reverse 1..40) {last if $i < length($long); if
> (substr($prev, 0, $i) eq substr($n, 0, $i)) {$long = substr($prev, 0, $i);
> last} } $prev = $n; END {say $long}'
Ooh, object-collision golf.
Try:
git cat-file --batch-all-objects --batch-check='%(objectname)'
instead of "rev-list | sort". It's _much_ faster, because it doesn't
have to actually open the objects and walk the graph.
Some versions of uniq have "-w" (including GNU, but it's definitely not
in POSIX), which lets you do:
git cat-file --batch-all-objects --batch-check='%(objectname)' |
uniq -cdw 7
to list all collisions of length 7 (it will show just the first item
from each group, but you can use -D to see them all).
> > You'll always need to list them all. It's inherently an operation where
> > for each SHA-1 you need to search for other ones with that prefix up to
> > a given length.
> >
> > Perhaps you've missed that you can use --abbrev=N for this, and just
> > grep for things that are loger than that N, e.g. for linux.git:
> >
> > git log --oneline --abbrev=10 --pretty=format:%h |
> > grep -E -v '^.{10}$' |
> > perl -pe 's/^(.{10}).*/$1/'
>
> I think the goal was to search all object hashes, not just commits. And git
> rev-list --objects will do that.
You can add "-t --raw" to see the abbreviated tree and blob names,
though it gets tricky around handling merges.
-Peff
