Load project-specific "start" hooks before our checks

Read from the project ".hooks-config" a configuration value

 hooks.start.commit-msg
 hooks.start.pre-commit
 hooks.start.prepare-commit-msg

to run from our respective hook before its main checks.

commit-msg

@@ -17,6 +17,9 @@
 
 . "${BASH_SOURCE%/*}/hooks-config.bash"
 
+# Start with project-specific hook.
+hooks_start commit-msg "$@"
+
 # Prepare a copy of the message:
 #  - strip comment lines
 #  - stop at "diff --git" (git commit -v)

hooks-config.bash

@@ -43,6 +43,12 @@ hooks_chain() {
 	hooks_child "$chain" "$@" || exit
 }
 
+hooks_start() {
+	hook="$1" ; shift
+	start="$(hooks_config --get hooks.start.$hook)"
+	hooks_child "$start" "$@" || exit
+}
+
 hooks_child() {
 	child="$1" ; shift
 	test -n "$child" || return 0

pre-commit

@@ -17,6 +17,9 @@
 
 . "${BASH_SOURCE%/*}/hooks-config.bash"
 
+# Start with project-specific hook.
+hooks_start pre-commit "$@"
+
 die() {
 	echo 'pre-commit hook failure' 1>&2
 	echo '-----------------------' 1>&2

prepare-commit-msg

@@ -17,6 +17,9 @@
 
 . "${BASH_SOURCE%/*}/hooks-config.bash"
 
+# Start with project-specific hook.
+hooks_start prepare-commit-msg "$@"
+
 # Invoke the Gerrit Change-Id hook here for "git merge" because
 # it does not run the normal commit-msg hook.
 hooks_GerritId=$(git config --get hooks.GerritId)