Compare file to another file in another commit

Question

I have moved some code from a file to another file, and applied little changes in it. I would like to have a diff to see those changes.

The problem seems pretty common to me, but I have never needed to do such a thing. I only know how to compare the same file with himself in a previous revision, or 2 different files in the same revision.

Are there git diff options to compare one file in the current revision to another file in another commit? Or any other way?

Possible duplicate http://stackoverflow.com/questions/17563726/git-diff-for-one-commit — kravasb, Apr 16 '15 at 11:40
@kravasb I don't think it is a duplicate, I don't want to compare the whole commit to another commit, I just want the difference for that piece of code, so the new file compared to the other would be great — Joffrey, Apr 16 '15 at 11:45

score 3 · Accepted Answer · answered Apr 16 '15 at 11:51

3

I think this is what you are looking for. HEAD~3 can be replaced with the commit id.

git diff HEAD~3:oldfile.xml file/in/another/path/newfile.xml

answered Apr 16 '15 at 11:51

crea1

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Learned a new thing today. :-) – axiac Apr 16 '15 at 12:04

score 1 · Answer 2 · edited Jun 20 '20 at 09:12

A dirty but working solution

Use git ls-tree to get the SHA1 identifier of the files on the commits you want to compare then use git diff [options] <blob> <blob> and provide the two SHA1 identifiers as arguments.

$ git ls-tree commit1 dir1/dir2/file1.txt
100644 blob 7d252b754d46a8fcd0613a96710c9326942d7a92   dir1/dir2/file1.txt

$ git ls-tree commit2 dirA/fileB.txt
100644 blob 4d000ed739c880a26686a2843dae6eeeb4109a37   dirA/fileB.txt

$ git diff 7d252b754d46a8fcd0613a96710c9326942d7a92 4d000ed739c880a26686a2843dae6eeeb4109a37

If you need to do this frequently you can even pack everything in a small shell script:

#!/bin/bash

# This script does not validate its command line arguments!

COMMIT1=$1
FILE1=$2
COMMIT2=$3
FILE2=$4

BLOB1=$(git ls-tree $COMMIT1 $FILE1 | cut -f3 -d' ' | cut -f1)
BLOB2=$(git ls-tree $COMMIT2 $FILE2 | cut -f3 -d' ' | cut -f1)

git diff $BLOB1 $BLOB2

Run it as:

$ script.sh commit1 dir1/dir2/file1.txt commit2 dirA/fileB.txt

indeed @crea1 's solution looks like the way to go, thank you for the effort anyway! — Joffrey, Apr 16 '15 at 12:12

Compare file to another file in another commit

2 Answers2

A dirty but working solution