fix SConstruct so that it can build from a git checkout rather than an svn checkout

git-svn-id: svn://localhost/ardour2/branches/3.0@3888 d708f5d6-7413-0410-9779-e7cbd77b26cf

SConstruct

@@ -257,9 +257,36 @@ def fetch_svn_revision (path):
     cmd += " | awk '/^Revision:/ { print $2}'"
     return commands.getoutput (cmd)
 
+def fetch_git_revision (path):
+    cmd = "LANG= "
+    cmd += "git log --abbrev HEAD^..HEAD "
+    cmd += path
+    output = commands.getoutput (cmd)
+    output = output.splitlines()
+
+    rev = output[0].replace( "commit", "git")[0:7]
+    for line in output:
+    	try:
+	    if "git-svn-id" in line:
+		line = line.split('@')
+		line = line[1].split(' ')
+		rev = line[0]
+	except:
+	    pass
+
+    return rev
+
 def create_stored_revision (target = None, source = None, env = None):
+    rev = ""
     if os.path.exists('.svn'):    
         rev = fetch_svn_revision ('.');
+    elif os.path.exists('.git'):
+        rev = fetch_git_revision ('.');
+    else:
+        print "You cannot use \"scons revision\" on without using a checked out"
+        print "copy of the Ardour source code repository"
+        sys.exit (-1)
+
     try:
 	text  = "#include <ardour/svn_revision.h>\n"
 	text += "namespace ARDOUR {\n";
@@ -272,10 +299,6 @@ def create_stored_revision (target = None, source = None, env = None):
     except IOError:
 	print "Could not open libs/ardour/svn_revision.cc for writing\n"
 	sys.exit (-1)
-    else:
-        print "You cannot use \"scons revision\" on without using a checked out"
-        print "copy of the Ardour source code repository"
-        sys.exit (-1)
 
 #
 # A generic builder for version.cc files