Are binary xdeltas only used if you use git-gc?

["Thanassis Tsiodras" <ttsiodras@gmail.com>]

Hi everyone.

I've been usig Git for the last couple of months and am quite happy with it.
In one of my Git repositories, I am storing uncompressed .tar files
(since being uncompressed allows git to detect and store
only their "real"differences).

However, when I introduce a new filename in the repos (with a minor
set of differences compared to an existing file with a different filename)
I've been unsuccessful in finding a way to tell Git to do it efficiently...

This is what I mean:

bash$ mkdir -p /var/tmp/tst
bash$ cd /var/tmp/tst
bash$ git init
bash$ cp /var/www/renderer-2.0e.tar .
bash$ git add renderer-2.0e.tar
bash$ git commit -m "First version"
bash$ du -s -k .git/
1724    .git/
bash$ cp renderer-2.0e.tar renderer-2.0f.tar
bash$ git add renderer-2.0f.tar
bash$ git commit -m "To add new version, first copy the first, so Git
detects it"
bash$ du -s -k .git/
1740    .git/
bash$ echo Good, Git detected it is the same
bash$ cp /var/www/renderer-2.0f.tar .
bash$ git add renderer-2.0f.tar
bash$ git commit -m "Real new version, slightly different to first"
bash$ du -s -k .git/
3344    .git/
bash$ echo What... did I do something wrong
bash$ xdelta delta renderer-2.0e.tar renderer-2.0f.tar delta
bash$ ls -l
total 7788
-rw-r--r-- 1 ttsiod ttsiod    8181 2008-10-31 11:27 delta
-rw-r--r-- 1 ttsiod ttsiod 3962880 2008-10-31 11:23 renderer-2.0e.tar
-rw-r--r-- 1 ttsiod ttsiod 3993600 2008-10-31 11:25 renderer-2.0f.tar
bash$ git-gc
bash$ du -s -k .git/
1660    .git/

So even though the xdelta is just 8KB, and git-gc actually finds out
that indeed
the new file is very similar to the old one, the initial commit of the
new version
in the repos is not taking advantage.

I found out about this when I tried to "git push" over a PSTN modem...

Then again, I must confess I only did the git-gc after I pushed.
Does the git-push actually take advantage of the similarities only if
I do a git-gc first?

If that is the case, I will create an alias to always git-gc after commits...

--
What I gave, I have; what I spent, I had; what I kept, I lost. -Old Epitaph