Several git commands are implemented as shell scripts that run awk, sed, grep
and perl. There is some existing patching in the postinstall for perl to rewrite
it to an absolute reference to pkgs.perl, but several other packages are both
missing as a dependency and have no rewrite logic.
In particular git filter-branch depends on sed and grep.
Additionally, the perl logic also seds git-am, which is now a binary not a shell
script anymore (see <github.com/git/git/blob/master/builtin/am.c>), so this part
was obsolete.
I tested this by grepping all shell scripts for the relevant commands and then
comparing the diffs of the new version to what is produced in master. All
changes in the scripts seem good to me.
2c1097a83b