add hack-gdbinit Makefile target

This target adds the needed "source" line to your ~/.gdbinit so that
this extension will always be available.

Makefile

@@ -9,3 +9,10 @@ gui/fix_signals.so: gui/fix-signals.c
 
 clean:
 	-rm SourceMe.py gui/fix_signals.so
+
+hack-gdbinit:
+	if test -f $$HOME/.gdbinit && `grep -q SourceMe $$HOME/.gdbinit`; then \
+	  :; \
+	else \
+	  echo "source `pwd`/SourceMe.py" >> $$HOME/.gdbinit; \
+	fi

README

@@ -25,7 +25,9 @@ On Fedora I think this suffices:
     sudo yum install gdb python-devel gtksourceview3 pygobject3
 
 After you install this, type "make".  Now, start gdb and source the
-"SourceMe.py" file.  This sets everything up.
+"SourceMe.py" file.  This sets everything up.  If you want it to
+always be available, you can use "make hack-gdbinit", which will add
+the appropriate "source" line to your ~/.gdbinit.
 
 This adds a new "gui" command to gdb.  Currently the only subcommand
 is "gui source", which pops up a source window.  The source window