How to speedup git clone for big binary files (disable delta compression)

["René Scheibe" <rene.scheibe@gmail.com>]

Hi,

I was wondering why "git clone" seems to not respect "-delta" in .gitattributes.


*Reproduction*

I prepared a test repository with:

- git v2.17.1
- .gitattributes containing "*.bin binary -delta"
- 10 commits with a 10 MB random binary file

Code:
---------------------------------------------------------------------
#!/bin/bash

# setup repository
git init --quiet repo
cd repo

echo '*.bin binary -delta' > .gitattributes
git add .gitattributes
git commit --quiet -m 'attributes'

for i in $(seq 10); do
    dd if=/dev/urandom of=data.bin bs=1MB count=10 status=none
    git add data.bin
    git commit --quiet -m "data $i"
done
cd ..

# create clone repository
time git clone --no-local repo clone

# repack original repository
cd repo
time git repack -a -d
---------------------------------------------------------------------

Output:
---------------------------------------------------------------------
Cloning into 'clone'...
remote: Counting objects: 33, done.
remote: Compressing objects: 100% (31/31), done.
remote: Total 33 (delta 0), reused 0 (delta 0)
Receiving objects: 100% (33/33), 95.40 MiB | 19.94 MiB/s, done.

real    0m25,085s
user    0m22,749s
sys     0m0,948s

Counting objects: 33, done.
Delta compression using up to 2 threads.
Compressing objects: 100% (21/21), done.
Writing objects: 100% (33/33), done.
Total 33 (delta 0), reused 0 (delta 0)

real    0m5,652s
user    0m4,173s
sys     0m0,178s
---------------------------------------------------------------------


*Observations*

_time_

- Cloning: "clone" takes always 25s
- Optimizing: "repack" takes 25s with and 5s without delta compression

_compressed objects_

- Cloning: "clone" compresses always 31 objects
- Optimizing: "repack" compresses 31 objects with and 21 objects without delta compression


*Expectations*

Both operations ("repack" and "clone") are using "pack-objects".

Therefore my expectation is that "clone" should respect "-delta" and be about as fast as "repack".


Cheers,
  René