Avoid using a lot of memory when large objects are present in the git repository

.. and have to be checked to see if they are a pointed to an annexed file.

Cases where such memory use could occur included, but were not limited to:
  - git commit -a of a large unlocked file (in v5 mode)
  - git-annex adjust when a large file was checked into git directly
Generally, any use of catKey was a potential problem.

Fix by using git cat-file --batch-check to check size before catting.
This adds another git batch process, which is included in the CatFileHandle
for simplicity.

There could be performance impact, anywhere catKey is used. Particularly
likely to affect adjusted branch generation speed, and operations on
unlocked files in v6 mode. Hopefully since the --batch-check and
--batch read the same data, disk buffering will avoid most overhead.
Leaving only the overhead of talking to the process over the pipe and
whatever computation --batch-check needs to do.

This commit was sponsored by Bruno BEAUFILS on Patreon.

1 files changed, 6 insertions, 0 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 15a5de2f5..57c497495 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -17,6 +17,12 @@ git-annex (6.20160924) UNRELEASED; urgency=medium
   * Linux standalone: Include locale files in the bundle, and generate
     locale definition files for the locales in use when starting runshell.
     (Currently only done for utf-8 locales.)
+  * Avoid using a lot of memory when large objects are present in the git
+    repository and have to be checked to see if they are a pointed to an
+    annexed file. Cases where such memory use could occur included, but
+    were not limited to:
+    - git commit -a of a large unlocked file (in v5 mode)
+    - git-annex adjust when a large file was checked into git directly
 
  -- Joey Hess <id@joeyh.name>  Mon, 26 Sep 2016 16:46:19 -0400