Unexpected behavior with git filters and signed commits

Question

Consider the following example.

mkdir pgp-git-test
cd pgp-git-test
git init
touch a.txt
git add a.txt
git commit -m "Add a.txt" -S
touch b.txt
git add b.txt
git commit -m "Add b.txt" -S
git filter-branch --index-filter 'git rm --cached --ignore-unmatch a.txt' --prune-empty HEAD
git log --oneline --decorate
b4efdf0 (HEAD -> master)  iQIcBAABCgAGBQJVrvqHAAoJEGuo23L9/VuyntUQAIBD0g03rTKRkOd9eM4bJgUV  jJezu7R4J0U+zVLrsrSl8oTrYrKPL5QAIqqaB9978qSx5WsmCJj8EfIZ2lwFj7kI  sWWcqjAWcRjWrte/v7ehUyTpJF6h5mWJPbC31BueZ3qlVvvfI03NbMUGocm1VOvE  KZakYkbhrA4ucA0K0YH9RKFo59cLS48SB7DQK4dBfdJSOnBC0Ga9pgBp8wnF2TQG  znRA3MnGRPJMRxZsend5P6gyeGl3wo0J/yk8HDFZXudTRS3SLB+um3NcTXRLIE9Z  Whud2oERKE9CuHU8Y64prbKKA27vWgaVQOC44ujaCqbYXuq+4Ozs34PBlf3CjJqW  19GdVBlqFfiyCPULwyxoPWkRk2kPQyEejt+sJIXG9QgefvoqFF5oLW/YA7AOrDSE  luLbC8uxmTARCWGZVGINL7NmPmEVFDZVj9EyYOjxE/+0wm4cGNBHrL6/JMkVOgpT  pWlgZWR3rX4IjzYtN6DMqKYNWVkVawZQUPh5n5jteuripWtnu5IG8vvvK2mtlkQ3  1OZIdQNAv0HYhBO0vHlV0o2TlVL5x9WfPFn+1XJepJUcoN3MdzXLxN27njdW5Bti  olEqyHrTRxYJNZgSwpQ7WITheIFDqpdcoUV2h4hNjGcXfc0DfaevtCA/oQir+3L4  JlFB35Le9Yby9htVhlu2  =RJi9  -----END PGP SIGNATURE-----
9f82e63  iQIcBAABCgAGBQJVrvp7AAoJEGuo23L9/Vuy/3QP/itaNGwRtlPB4uajGGHMUPxn  gnzd5k5gaWvWlE0Cn/v+CFqE9zVfNiqfsEwJ5YUycUNtEuF9rsiqeQWaWdHWquqr  kOEwRx/9mliK7iC2MZBn/biY5wBE2VcO2m281SnCKxslCjHJxlBo9rglq1t0wybT  CX7C7ScKAtYkos4c1vL0D5Bam2panVXs/KT/YDgWZT9kTg+lEd7NaIwxxNn7HNs7  sOvI2zLyca2FepahF99ZRGg1kKXarVh9nW4mZ1GfeAUuCNSwgwBv+NO3wFC1Blcp  uzKAo1F/cN0rAOr0bMdIZ0qJEVMBBpaqodqRqCOcmYTm5CoKFmcNJvixPl+hYsQx  mPFxM0yVsjlLAnIckNqos/T3i6T8zrb5X4g5ZwuQZzzNKy1xx809v9erb2HHK+d1  +MqdzwEcMyGqfyhz9s1BGrwpBk5CAg2MXbtPpoMTBIG7hmke1al89jvgBiuir06E  kEN6jl/2yAfsj7k5ryjFQNSPJ+HYEyvYBCx3u+xXdA5IBH6CU2S44RqugwztbVKz  /Viel4wIHJ8UCA85ZiprRWJE+nz1RXKlBZc/37W4vcSUSTELXEkhaybOM/eBKACR  sDHOKq5MG9VmZXcu0Zs0cyEvuqljSnZggbDasXHj68b86rB5VRGIO10ad1xKPnFZ  PTUmKKtz1NZkMmjIX4vR  =Mnxi  -----END PGP SIGNATURE-----

I have two questions. First, why doesn't this remove the first commit from the log? And secondly, why is the PGP signature now at the top of the commit message and is there a way to avoid this when using git filter-branch?

(In case that matters, I use git v. 2.4.6.)

Answer 1

I have no answer as to why the first team was not removed from the story in this toy example.

, , , . PGP git filter-branch, - , , , .

, , .

, - iQIcBA, , .

git filter-branch --msg-filter 'sed "/iQIcBA.*/,/.*END PGP SIGNATURE.*/d"' HEAD

, - .

git filter-branch --commit-filter 'git commit-tree -S "$@"' HEAD

, (., , ).

---

^git.

Answer 2

. :

,

https://git-scm.com/docs/git-filter-branch

.

• .
• .

a.txt .

( ) .

, : https://github.com/git/git/blob/master/git-filter-branch.sh#L410

, . , , test $# = 3, , : https://github.com/git/git/blob/master/git-filter-branch.sh#L47

, else, .

, , "$1" = $(git rev-parse "$3^{tree}"), sha sha , .

, , . , . , , SHELL.

, ​​ PGP. , , , , , , .