Merge branch 'jc/show-sig'

* jc/show-sig:
  log --show-signature: reword the common two-head merge case
  log-tree: show mergetag in log --show-signature output
  log-tree.c: small refactor in show_signature()
  commit --amend -S: strip existing gpgsig headers
  verify_signed_buffer: fix stale comment
  gpg-interface: allow use of a custom GPG binary
  pretty: %G[?GS] placeholders
  test "commit -S" and "log --show-signature"
  log: --show-signature
  commit: teach --gpg-sign option

Conflicts:
	builtin/commit-tree.c
	builtin/commit.c
	builtin/merge.c
	notes-cache.c
	pretty.c

Documentation/RelNotes/1.7.9.txt

@@ -99,10 +99,6 @@ Unless otherwise noted, all the fixes since v1.7.8 in the maintenance
 releases are contained in this release (see release notes to them for
 details).
 
- * gitweb did not correctly fall back to configured $fallback_encoding
-   that is not 'latin1'.
-   (merge b13e3ea jn/maint-gitweb-utf8-fix later to maint).
-
 --
 exec >/var/tmp/1
 O=v1.7.8.2-301-g48de656