Fix space-prefixed commit header line handling in decoding

[sttts]

GPG signatures (and maybe other commit header extensions) use space-prefixes lines for multi-line values. Compare e.g. (with $ as the line end):

> git show --format=raw 7b8bb6e7d3345b04678d96a721f651a4a68eb1dd | sed 's/$/$/'
commit 7b8bb6e7d3345b04678d96a721f651a4a68eb1dd$
tree 45c1bcc6a707d9060419cc169484f511cd3baf20$
parent d723028d09d2fd3faa177782de8e444ac64f5875$
parent f952b093a7faa62323617a684e7f6a58d863f42f$
author Kubernetes Submit Queue <k8s-merge-robot@users.noreply.github.com> 1526444292 -0700$
committer GitHub <noreply@github.com> 1526444292 -0700$
gpgsig -----BEGIN PGP SIGNATURE-----$
 $
 wsBcBAABCAAQBQJa+7EECRBK7hj4Ov3rIwAAdHIIAACfUDQrBSxbrKOdxPVDJh31$
 S6ZvJjmEp3ha3p59YqJ740SWvdKbykb2IreMUHuIFV87N0OHlh1SonSiZKlANC7z$
 QyZcfS7O6PTMnRaLpHlLkV3rTr0gE0aNmiokFCpJJF1l0ULHv5H4OLOktNWrISdO$
 kFNrBSmqlbmndBTRQoMMaRSD9W71VqzDn9rFcPqkaz+Fu0NX7ztIwyUQQ1gcvpto$
 fowgR3TiOaUMci0lXRdv2aPchBHYHhidPTe6x5HDtciEd+LX0R2d3w2JnXaeuzKQ$
 x4M35+xt3bC3SG9dWPVyPi0nV+pMTfdHNJqLehNZQayBSSHfMeQ3TaybOyBJF8E=$
 =HoUx$
 -----END PGP SIGNATURE-----$
 $
$
    Merge pull request #63357 from Random-Liu/install-and-use-crictl$

[sttts]

/cc @nikhita

[jfontan]

@sttts it would be nice to have an additional test that checks this case.

[mcuadros]

Can you provide a test? Thanks

[sttts]

This was fixed already in #892. Closing.

[sttts]

This was fixed already in #892. Closing.