py-compile: normalize error and help messages

* lib/py-compile: Now error messages do not begin with a capital
letter, nor end with a period, as per GNU standards.  Prepend the
error messages with the name of the script, not with its path.
When an invalid usage is recognized, always display the customary
message "Try `py-compile --help' ..." on a line of its own.
($me): New variable, containing the name of the
program, i.e., `py-compile'.  Use it throughout.
(usage_error): New function, used to display error messages about
invalid usage.
* tests/py-compile-usage.test: Extend and tighten accordingly.

1 files changed, 13 insertions, 7 deletions

diff --git a/lib/py-compile b/lib/py-compile
index 2a526cab7..140536bd1 100755
--- a/lib/py-compile
+++ b/lib/py-compile
@@ -32,6 +32,15 @@ if [ -z "$PYTHON" ]; then
   PYTHON=python
 fi
 
+me=py-compile
+
+usage_error ()
+{
+  echo "$me: $*" >&2
+  echo "Try \`$me --help' for more information." >&2
+  exit 1
+}
+
 basedir=
 destdir=
 files=
@@ -39,8 +48,7 @@ while test $# -ne 0; do
   case "$1" in
     --basedir)
       if test $# -lt 2; then
-        echo "$0: Missing argument to --basedir." 1>&2
-        exit 1
+        usage_error "option '--basedir' requires an argument"
       else
         basedir=$2
       fi
@@ -48,8 +56,7 @@ while test $# -ne 0; do
       ;;
     --destdir)
       if test $# -lt 2; then
-        echo "$0: Missing argument to --destdir." 1>&2
-        exit 1
+        usage_error "option '--destdir' requires an argument"
       else
         destdir=$2
       fi
@@ -72,7 +79,7 @@ EOF
       exit $?
       ;;
     -v|--v*)
-      echo "py-compile $scriptversion"
+      echo "$me $scriptversion"
       exit $?
       ;;
     *)
@@ -83,8 +90,7 @@ EOF
 done
 
 if test -z "$files"; then
-    echo "$0: No files given.  Try \`$0 --help' for more information." 1>&2
-    exit 1
+    usage_error "no files given"
 fi
 
 # if basedir was given, then it should be prepended to filenames before