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filter-branch: remove multi-line headers in msg filter

PATCH In review James McCoy 3 participants 5 messages Jun 15, 2016

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James McCoy

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#0 lore raw

PATCH v2 1/1 filter-branch: remove multi-line headers in msg filter

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 <[email protected]> 1112912413 -0700
  committer C O Mitter <[email protected]> 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 <[email protected]>
---
 git-filter-branch.sh     |  2 +-
 t/t7003-filter-branch.sh | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
git-filter-branch.sh +1 -1
index 5b3f63d..fff8093 100755
@@ -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...
 			:;
t/t7003-filter-branch.sh +14 -0
index 855afda..377c648 100755
@@ -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 &&
Signature · 6 lines
2.6.1


-- 
James
GPG Key: 4096R/331BA3DB 2011-12-05 James McCoy <[email protected]>
Reviewed-by on v2 1/1
#1 lore raw

James McCoy venit, vidit, dixit 09.10.2015 02:21:

Quoted 34 lines

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 <[email protected]> 1112912413 -0700
  committer C O Mitter <[email protected]> 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.

Quoted 7 lines

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 <[email protected]>

---

Thanks for hanging in :)

Reviewed-by Michael J Gruber <[email protected]>
#2 lore raw
Quoted 11 lines · Michael J Gruber
Quoted 7 lines

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 <[email protected]>

---

Thanks for hanging in :)

Reviewed-by Michael J Gruber <[email protected]>

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.

#3 lore raw

Junio C Hamano venit, vidit, dixit 09.10.2015 19:53:

Quoted 10 lines
Quoted 8 lines · Michael J Gruber
Quoted 7 lines

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 <[email protected]>

---

Quoted 7 lines
Quoted 3 lines

Thanks for hanging in :)

Reviewed-by Michael J Gruber <[email protected]>

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 <[email protected]>

in case that is needed or preferred.

Michael

#4 lore raw
Quoted 6 lines · Michael J Gruber

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 <[email protected]>

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.