add test-git-ignore.py, to port the 'clean' buildbot test to git

add .gitignore to match .darcs-boringfile, mostly

.gitignore

@@ -0,0 +1,22 @@
+*.pyc
+*.pyo
+
+/build/
+/support/
+
+# these are generated at build time, and never checked in
+/src/allmydata/_version.py
+/src/allmydata/_appname.py
+
+# these are generated too
+/bin/tahoe
+/bin/tahoe.pyscript
+/bin/tahoe-script.py
+
+/.built
+/src/allmydata_tahoe.egg-info/
+Twisted-*.egg
+
+/_trial_temp*
+/dist/
+/twisted/plugins/dropin.cache

Makefile

@@ -209,6 +209,10 @@ test-darcs-boringfile:
 	$(MAKE)
 	$(PYTHON) misc/build_helpers/test-darcs-boringfile.py
 
+test-git-ignore:
+	$(MAKE)
+	$(PYTHON) misc/build_helpers/test-git-ignore.py
+
 test-clean:
 	find . |grep -vEe "_darcs|allfiles.tmp|src/allmydata/_(version|appname).py" |sort >allfiles.tmp.old
 	$(MAKE)

misc/build_helpers/test-git-ignore.py

@@ -0,0 +1,14 @@
+#!/usr/bin/env python
+
+import sys
+from subprocess import Popen, PIPE
+
+cmd = ["git", "status", "--porcelain"]
+p = Popen(cmd, stdout=PIPE)
+output = p.communicate()[0]
+print output
+if output == "":
+    sys.exit(0)
+sys.exit(1)
+
+