bug? 'git log -M100' is different from 'git log -M100%'

Hi,

When using -M with a number to act as a threshold for declaring a change as being a rename, I found a... quirk. Any 2-digit number after the M will work, but if the number is 100, it will require a % to be appended to be effective.

Here's a transcript that will demonstrate the problem when run in an empty directory.

    # setup
    git init
    seq 1 100 > f1
    git add f1
    git commit -m f1
    git rm f1
    ( seq 1 45; seq 1001 1010; seq 56 100 ) > f2
    git add f2
    git commit -m f2

    # here's the buglet

    git log -1 --stat --raw -M
    # this tells you the files are 83% similar

    git log -1 --stat --raw -M82
    # this shows it like a rename

    git log -1 --stat --raw -M83
    # this also

    git log -1 --stat --raw -M84
    # this shows two separate files

    git log -1 --stat --raw -M99
    # this also

    # so far so good...

    git log -1 --stat --raw -M100
    # but this shows it like a rename

    git log -1 --stat --raw -M100%
    # adding a percent sign fixes it, now they're two separate
    # files.  It seems to be required only when you ask for 100%

Sitaram Chamarty <sitaramc@gmail.com> writes:

That is not 2-digit number.

A few historical trivia may help.

Originally we said "you can use -M2 to choose 2/10" (like "gzip" taking compression levels between "-0" to "-9"). Then Linus came up with a clever idea to let people specify arbitrary precision by letting you say "-M25" to mean 25/100 and "-M254" to mean 254/1000.

Read the numbers without per-cent as if it has decimal point before it (i.e. -M005 is talking about 0.005 which is 0.5%). Full hundred per-cent has to be spelled with per-cent sign for obvious reasons with this scheme but that cannot be avoided. It is a special case.

On Tue, Dec 18, 2012 at 6:55 AM, Junio C Hamano <gitster@pobox.com> wrote:

Oh nice.  Makes sense; thanks!

I submitted a patch to diff-options.txt (separately).

regards

sitaram