Enforce function declaration format in bash8

Check that function calls look like ^function foo {$ in bash8, and fix
all existing failures of that check.  Add a note to HACKING.rst

Change-Id: Ic19eecb39e0b20273d1bcd551a42fe400d54e938
diff --git a/tools/info.sh b/tools/info.sh
index 1e521b9..a8f9544 100755
--- a/tools/info.sh
+++ b/tools/info.sh
@@ -61,7 +61,7 @@
 # -----
 
 # git_report <dir>
-function git_report() {
+function git_report {
     local dir=$1
     local proj ref branch head
     if [[ -d $dir/.git ]]; then