How does one extract a unified-diff style patch subset?

Question

Every time I want to take a subset of a patch, I'm forced to write a script to only extract the indices that I want.

e.g. I have a patch that applies to sub directories 'yay' and 'foo'.

Is there a way to create a new patch or apply only a subset of a patch? i.e. create a new patch from the existing patch that only takes all indices that are under sub directory 'yay'. Or all indices that are not under sub directory 'foo'

If I have a patch like ( excuse the below pseudo-patch):

Index : foo/bar
 yada
 yada
- asdf
+ jkl
 yada
 yada
Index : foo/bah
 blah
 blah
- 28
+ 29
 blah
 blah
 blah
Index : yay/team
 go
 huskies
- happy happy
+ joy joy
 cougars
 suck

How can I extract or apply only the 'yay' subdirectory like:

Index : yay/team
 go
 huskies
- happy happy
+ joy joy
 cougars
 suck

I know if I script up a solution I'll be re-inventing the wheel...

Answer 1

Here's my quick and dirty Perl solution.

perl -ne '@a = split /^Index :/m, join "", <>; END { for(@a) {print "Index :", $_ if (m, yay/team,)}}' < foo.patch

Answer 2

Take a look at the filterdiff utility, which is part of patchutils.

For example, if you have the following patch:

$ cat example.patch
diff -Naur orig/a/bar new/a/bar
--- orig/a/bar  2009-12-02 12:41:38.353745751 -0800
+++ new/a/bar   2009-12-02 12:42:17.845745951 -0800
@@ -1,3 +1,3 @@
 4
-5
+e
 6
diff -Naur orig/a/foo new/a/foo
--- orig/a/foo  2009-12-02 12:41:32.845745768 -0800
+++ new/a/foo   2009-12-02 12:42:25.697995617 -0800
@@ -1,3 +1,3 @@
 1
 2
-3
+c
diff -Naur orig/b/baz new/b/baz
--- orig/b/baz  2009-12-02 12:41:42.993745756 -0800
+++ new/b/baz   2009-12-02 12:42:37.585745735 -0800
@@ -1,3 +1,3 @@
-7
+z
 8
 9

Then you can run the following command to extract the patch for only things in the a directory like this:

$ cat example.patch | filterdiff -i 'new/a/*'
--- orig/a/bar  2009-12-02 12:41:38.353745751 -0800
+++ new/a/bar   2009-12-02 12:42:17.845745951 -0800
@@ -1,3 +1,3 @@
 4
-5
+e
 6
--- orig/a/foo  2009-12-02 12:41:32.845745768 -0800
+++ new/a/foo   2009-12-02 12:42:25.697995617 -0800
@@ -1,3 +1,3 @@
 1
 2
-3
+c

Answer 3

In response to sigjuice's request in the comments, I'm posting my script solution. It isn't 100% bullet proof, and I'll probably use filterdiff instead.

base_usage_str=r'''
    python %prog index_regex patch_file

description:
    Extracts all indices from a patch-file matching 'index_regex'

    e.g.
        python %prog '^evc_lib' p.patch > evc_lib_p.patch

        Will extract all indices which begin with evc_lib.

        -or-

        python %prog '^(?!evc_lib)' p.patch > not_evc_lib_p.patch

        Will extract all indices which do *not* begin with evc_lib.

authors:
    Ross Rogers, 2009.04.02
'''

import re,os,sys
from optparse import OptionParser

def main():

    parser = OptionParser(usage=base_usage_str)

    (options, args) = parser.parse_args(args=sys.argv[1:])

    if len(args) != 2:
        parser.print_help()
        if len(args) == 0:
            sys.exit(0)
        else:
            sys.exit(1)

    (index_regex,patch_file) = args
    sys.stderr.write('Extracting patches for indices found by regex:%s\n'%index_regex)
    #print 'user_regex',index_regex
    user_index_match_regex = re.compile(index_regex)

    # Index: verification/ring_td_cte/tests/mmio_wr_td_target.e
    # --- sw/cfg/foo.xml      2009-04-30 17:59:11 -07:00
    # +++ sw/cfg/foo.xml      2009-05-11 09:26:58 -07:00

    index_cre = re.compile(r'''(?:(?<=^)|(?<=\n))(--- (?:.*\n){2,}?(?![ @\+\-]))''')

    patch_file = open(patch_file,'r')
    all_patch_sets = index_cre.findall(patch_file.read())
    patch_file.close()

    for file_edit in all_patch_sets:
        # extract index subset
        index_path = re.compile('\+\+\+ (?P<index>[\w_\-/\.]+)').search(file_edit).group('index').strip()
        if user_index_match_regex.search(index_path):
            sys.stderr.write("Index regex matched index: "+index_path+"\n")
            print file_edit,


if __name__ == '__main__':
    main()