[PATCH v2] filter-branch: remove multi-line headers in msg filter

[PATCH v2] filter-branch: remove multi-line headers in msg filter

[James McCoy]

df062010 (filter-branch: avoid passing commit message through sed)
introduced a regression when filtering commits with multi-line headers,
if the header contains a blank line.  An example of this is a gpg-signed
commit:

  $ git cat-file commit signed-commit
  tree 3d4038e029712da9fc59a72afbfcc90418451630
  parent 110eac945dc1713b27bdf49e74e5805db66971f0
  author A U Thor <author@example.com> 1112912413 -0700
  committer C O Mitter <committer@example.com> 1112912413 -0700
  gpgsig -----BEGIN PGP SIGNATURE-----
   Version: GnuPG v1

   iEYEABECAAYFAlYXADwACgkQE7b1Hs3eQw23CACgldB/InRyDgQwyiFyMMm3zFpj
   pUsAnA+f3aMUsd9mNroloSmlOgL6jIMO
   =0Hgm
   -----END PGP SIGNATURE-----

  Adding gpg

As a consequence, "filter-branch --msg-filter cat" (which should leave the
commit message unchanged) spills the signature (after the internal blank
line) into the original commit message.

The reason is that although the signature is indented, making the line a
whitespace only line, the “read” call is splitting the line based on
the shell's IFS, which defaults to <space><tab><newline>.  The leading
space is consumed and $header_line is empty, causing the “skip header
lines” loop to exit.

The rest of the commit object is then re-used as the rewritten commit
message, causing the new message to include the signature of the
original commit.

Set IFS to an empty string for the “read” call, thus disabling the word
splitting, which causes $header_line to be set to the non-empty value '
'.  This allows the loop to fully consume the header lines before
emitting the original, intact commit message.

Signed-off-by: James McCoy <vega.james@gmail.com>
---
 git-filter-branch.sh     |  2 +-
 t/t7003-filter-branch.sh | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index 5b3f63d..fff8093 100755
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -347,7 +347,7 @@ while read commit parents; do
 	fi
 
 	{
-		while read -r header_line && test -n "$header_line"
+		while IFS='' read -r header_line && test -n "$header_line"
 		do
 			# skip header lines...
 			:;
diff --git a/t/t7003-filter-branch.sh b/t/t7003-filter-branch.sh
index 855afda..377c648 100755
--- a/t/t7003-filter-branch.sh
+++ b/t/t7003-filter-branch.sh
@@ -2,6 +2,7 @@
 
 test_description='git filter-branch'
 . ./test-lib.sh
+. "$TEST_DIRECTORY/lib-gpg.sh"
 
 test_expect_success 'setup' '
 	test_commit A &&
@@ -292,6 +293,19 @@ test_expect_success 'Tag name filtering strips gpg signature' '
 	test_cmp expect actual
 '
 
+test_expect_success GPG 'Filtering retains message of gpg signed commit' '
+	mkdir gpg &&
+	touch gpg/foo &&
+	git add gpg &&
+	test_tick &&
+	git commit -S -m "Adding gpg" &&
+
+	git log -1 --format="%s" > expect &&
+	git filter-branch -f --msg-filter "cat" &&
+	git log -1 --format="%s" > actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'Tag name filtering allows slashes in tag names' '
 	git tag -m tag-with-slash X/1 &&
 	git cat-file tag X/1 | sed -e s,X/1,X/2, > expect &&
-- 
2.6.1


-- 
James
GPG Key: 4096R/331BA3DB 2011-12-05 James McCoy <jamessan@debian.org>

Re: [PATCH v2] filter-branch: remove multi-line headers in msg filter

[Michael J Gruber]

James McCoy venit, vidit, dixit 09.10.2015 02:21:
> df062010 (filter-branch: avoid passing commit message through sed)
> introduced a regression when filtering commits with multi-line headers,
> if the header contains a blank line.  An example of this is a gpg-signed
> commit:
> 
>   $ git cat-file commit signed-commit
>   tree 3d4038e029712da9fc59a72afbfcc90418451630
>   parent 110eac945dc1713b27bdf49e74e5805db66971f0
>   author A U Thor <author@example.com> 1112912413 -0700
>   committer C O Mitter <committer@example.com> 1112912413 -0700
>   gpgsig -----BEGIN PGP SIGNATURE-----
>    Version: GnuPG v1
> 
>    iEYEABECAAYFAlYXADwACgkQE7b1Hs3eQw23CACgldB/InRyDgQwyiFyMMm3zFpj
>    pUsAnA+f3aMUsd9mNroloSmlOgL6jIMO
>    =0Hgm
>    -----END PGP SIGNATURE-----
> 
>   Adding gpg
> 
> As a consequence, "filter-branch --msg-filter cat" (which should leave the
> commit message unchanged) spills the signature (after the internal blank
> line) into the original commit message.
> 
> The reason is that although the signature is indented, making the line a
> whitespace only line, the “read” call is splitting the line based on
> the shell's IFS, which defaults to <space><tab><newline>.  The leading
> space is consumed and $header_line is empty, causing the “skip header
> lines” loop to exit.
> 
> The rest of the commit object is then re-used as the rewritten commit
> message, causing the new message to include the signature of the
> original commit.
> 
> Set IFS to an empty string for the “read” call, thus disabling the word
> splitting, which causes $header_line to be set to the non-empty value '
> '.  This allows the loop to fully consume the header lines before
> emitting the original, intact commit message.
> 
> Signed-off-by: James McCoy <vega.james@gmail.com>
> ---

Thanks for hanging in :)

Reviewed-by: Michael J Gruber <git@drmicha.warpmail.net>

Re: [PATCH v2] filter-branch: remove multi-line headers in msg filter

[Junio C Hamano]

Michael J Gruber <git@drmicha.warpmail.net> writes:

>> Set IFS to an empty string for the “read” call, thus disabling the word
>> splitting, which causes $header_line to be set to the non-empty value '
>> '.  This allows the loop to fully consume the header lines before
>> emitting the original, intact commit message.
>> 
>> Signed-off-by: James McCoy <vega.james@gmail.com>
>> ---
>
> Thanks for hanging in :)
>
> Reviewed-by: Michael J Gruber <git@drmicha.warpmail.net>

As long as you are fine with giving authorship to James, I am fine
with that.  I'll amend what is queued with your reviewed-by above
and will merge to 'next'.

Thanks.

Re: [PATCH v2] filter-branch: remove multi-line headers in msg filter

[Michael J Gruber]

Junio C Hamano venit, vidit, dixit 09.10.2015 19:53:
> Michael J Gruber <git@drmicha.warpmail.net> writes:
> 
>>> Set IFS to an empty string for the “read” call, thus disabling the word
>>> splitting, which causes $header_line to be set to the non-empty value '
>>> '.  This allows the loop to fully consume the header lines before
>>> emitting the original, intact commit message.
>>>
>>> Signed-off-by: James McCoy <vega.james@gmail.com>
>>> ---
>>
>> Thanks for hanging in :)
>>
>> Reviewed-by: Michael J Gruber <git@drmicha.warpmail.net>
> 
> As long as you are fine with giving authorship to James, I am fine
> with that.  I'll amend what is queued with your reviewed-by above
> and will merge to 'next'.

Yep, I'm fine with "mini-mentoring", and just to be safe, the 7 new
characters in git-filter-branch.sh are (also)

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>

in case that is needed or preferred.

Michael

Re: [PATCH v2] filter-branch: remove multi-line headers in msg filter

[Junio C Hamano]

Michael J Gruber <git@drmicha.warpmail.net> writes:

> Yep, I'm fine with "mini-mentoring", and just to be safe, the 7 new
> characters in git-filter-branch.sh are (also)
>
> Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
>
> in case that is needed or preferred.

I was wondering if we want to do that or I can just add comments
"based on MJG's suggestion" or somesuch.  Most likely I'd do both
;-)

Thanks.