[RESEND PATCH v3 8/8] format-patch: read branch-specific output directory

If a user wishes to have a per-branch output directory for patches, they must manually specify this on the command-line with `-o` for each invocation of format-patch. However, this can be cumbersome for a user to keep track of. Read `format..outputDirectory` to give a branch-specific output direct

[PATCH v3 8/8] format-patch: read branch-specific output directory

If a user wishes to have a per-branch output directory for patches, they must manually specify this on the command-line with `-o` for each invocation of format-patch. However, this can be cumbersome for a user to keep track of. Read `format..outputDirectory` to give a branch-specific output direct