Git: show total file size difference between two commits?

Is it possible to show the total file size difference between two commits? Something like:

$ git file-size-diff 7f3219 bad418 # I wish this worked :)
-1234 bytes

I’ve tried:

$ git diff --patch-with-stat

And that shows the file size difference for each binary file in the diff — but not for text files, and not the total file size difference.

Any ideas?

git cat-file -s will output the size in bytes of an object in git. git diff-tree can tell you the differences between one tree and another.

Putting this together into a script called git-file-size-diff located somewhere on your PATH will give you the ability to call git file-size-diff <tree-ish> <tree-ish>. We can try something like the following:

#!/bin/bash
USAGE='[--cached] [<rev-list-options>...]

Show file size changes between two commits or the index and a commit.'

SUBDIRECTORY_OK=1
. "$(git --exec-path)/git-sh-setup"
args=$(git rev-parse --sq "$@")
[ -n "$args" ] || usage
cmd="diff-tree -r"
[[ $args =~ "--cached" ]] && cmd="diff-index"
eval "git $cmd $args" | {
  total=0
  while read A B C D M P
  do
    case $M in
      M) bytes=$(( $(git cat-file -s $D) - $(git cat-file -s $C) )) ;;
      A) bytes=$(git cat-file -s $D) ;;
      D) bytes=-$(git cat-file -s $C) ;;
      *)
        echo >&2 warning: unhandled mode $M in \"$A $B $C $D $M $P\"
        continue
        ;;
    esac
    total=$(( $total + $bytes ))
    printf '%d\t%s\n' $bytes "$P"
  done
  echo total $total
}

In use this looks like the following:

$ git file-size-diff HEAD~850..HEAD~845
-234   Documentation/RelNotes/1.7.7.txt
112    Documentation/git.txt
-4     GIT-VERSION-GEN
43     builtin/grep.c
42     diff-lib.c
594    git-rebase--interactive.sh
381    t/t3404-rebase-interactive.sh
114    t/test-lib.sh
743    tree-walk.c
28     tree-walk.h
67     unpack-trees.c
28     unpack-trees.h
total 1914

By using git-rev-parse it should accept all the usual ways of specifying commit ranges.

EDIT: updated to record the cumulative total. Note that bash runs the while read in a subshell, hence the additional curly braces to avoid losing the total when the subshell exits.

EDIT: added support for comparing the index against another tree-ish by using a --cached argument to call git diff-index instead of git diff-tree. eg:

$ git file-size-diff --cached master
-570    Makefile
-134    git-gui.sh
-1  lib/browser.tcl
931 lib/commit.tcl
18  lib/index.tcl
total 244

EDIT: Mark script as capable of running in a subdirectory of a git repository.