git-commit-vandalism/git-deltafy-script
Nicolas Pitre 53d4b46085 [PATCH] mkdelta enhancements (take 2)
Although it was described as such, git-mkdelta didn't really attempt to
find the best delta against any previous object in the list, but was
only able to create a delta against the preceeding object.  This patch
reworks the code to fix that limitation and hopefully makes it a bit
clearer than before, including fixing the delta loop detection which was
broken.

This means that

	git-mkdelta sha1 sha2 sha3 sha4 sha5 sha6

will now create a sha2 delta against sha1, a sha3 delta against either
sha2 or sha1 and keep the best one, a sha4 delta against either sha3,
sha2 or sha1, etc.  The --max-behind argument limits that search for the
best delta to the specified number of previous objects in the list.  If
no limit is specified it is unlimited (note: it might run out of
memory with long object lists).

Also added a -q (quiet) switch so it is possible to have 3 levels of
output: -q for nothing, -v for verbose, and if none of -q nor -v is
specified then only actual changes on the object database are shown.

Finally the git-deltafy-script has been updated accordingly, and some
bugs fixed (thanks to Stephen C. Tweedie for spotting them).

This version has been toroughly tested and I think it is ready
for public consumption.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-30 17:37:20 -07:00

68 lines
2.1 KiB
Bash
Executable File

#!/bin/bash
# Example script to deltafy an entire GIT repository based on the commit list.
# The most recent version of a file is the reference and previous versions
# are made delta against the best earlier version available. And so on for
# successive versions going back in time. This way the increasing delta
# overhead is pushed towards older versions of any given file.
#
# The -d argument allows to provide a limit on the delta chain depth.
# If 0 is passed then everything is undeltafied. Limiting the delta
# depth is meaningful for subsequent access performance to old revisions.
# A value of 16 might be a good compromize between performance and good
# space saving. Current default is unbounded.
#
# The --max-behind=30 argument is passed to git-mkdelta so to keep
# combinations and memory usage bounded a bit. If you have lots of memory
# and CPU power you may remove it (or set to 0) to let git-mkdelta find the
# best delta match regardless of the number of revisions for a given file.
# You can also make the value smaller to make it faster and less
# memory hungry. A value of 5 ought to still give pretty good results.
# When set to 0 or ommitted then look behind is unbounded. Note that
# git-mkdelta might die with a segmentation fault in that case if it
# runs out of memory. Note that the GIT repository will still be consistent
# even if git-mkdelta dies unexpectedly.
set -e
depth=
[ "$1" == "-d" ] && depth="--max-depth=$2" && shift 2
function process_list() {
if [ "$list" ]; then
echo "Processing $curr_file"
echo "$head $list" | xargs git-mkdelta $depth --max-behind=30 -v
fi
}
curr_file=""
git-rev-list HEAD |
git-diff-tree -r -t --stdin |
awk '/^:/ { if ($5 == "M" || $5 == "N") print $4, $6;
if ($5 == "M") print $3, $6 }' |
LC_ALL=C sort -s -k 2 | uniq |
while read sha1 file; do
if [ "$file" == "$curr_file" ]; then
list="$list $sha1"
else
process_list
curr_file="$file"
list=""
head="$sha1"
fi
done
process_list
curr_file="root directory"
head=""
list="$(
git-rev-list HEAD |
while read commit; do
git-cat-file commit $commit |
sed -n 's/tree //p;Q'
done
)"
process_list