Bug 799680 - Add a bash completion script for mach [r=gps]

DONTBUILD (not part of the build)

python/mach/bash-completion.sh

@@ -0,0 +1,30 @@
+function _mach()
+{
+  local cur cmds c subcommand mach
+  COMPREPLY=()
+
+  # Load the list of commands
+  mach=`which mach || echo ./mach`
+  cmds=`$mach mach-commands`
+
+  # Look for the subcommand.
+  cur="${COMP_WORDS[COMP_CWORD]}"
+  subcommand=""
+  c=1
+  while [ $c -lt $COMP_CWORD ]; do
+    word="${COMP_WORDS[c]}"
+    for cmd in $cmds; do
+      if [ "$cmd" = "$word" ]; then
+        subcommand="$word"
+      fi
+    done
+    c=$((++c))
+  done
+
+  if [[ "$subcommand" == "help" || -z "$subcommand" ]]; then
+      COMPREPLY=( $(compgen -W "$cmds" -- ${cur}) )
+  fi
+
+  return 0
+}
+complete -o default -F _mach mach