How do I "inverse" a diff file?

Question

Say I have a diff file looking basically like the following.

+line a
-line b

Is it possible to do one (or both) of the following:

Inverse this file (so I'd get)
```
-line a
+line b
```
Pass some argument to patch so the end result the same as applying the inversed diff file described above

You can change the order you put in the files. eg. diff a.txt b.txt -> diff b.txt a.txt. — matt, Feb 11 '16 at 19:25

score 7 · Answer 1 · answered Mar 05 '20 at 05:38

7

You can leave the diff as is and apply in reverse

git apply --reverse backwards-diff

answered Mar 05 '20 at 05:38

caduceus

score 6 · Answer 2 · answered Dec 11 '18 at 03:58

6

To rewrite a reversed / inverted diff file, use interdiff from diffutils:

interdiff -q my-diff-file /dev/null

answered Dec 11 '18 at 03:58

Tom Hale

score 5 · Answer 3 · answered Apr 20 '17 at 18:34

5

Here is what you should do (assuming newFile.txt is the file you want to apply the reversed diff file on and diffFile.txt is the diff file):

patch -R newFile.txt diffFile.txt -o oldFile.txt

answered Apr 20 '17 at 18:34

Mark Jin

3 Answers3