Add post upload hook to substitute hashtags for their mapped text

HASHTAGS

Index: HASHTAGS
diff --git a/HASHTAGS b/HASHTAGS
new file mode 100644
index 0000000000000000000000000000000000000000..5428a9c299bb54ad58241c273c63267c7dd149d9
--- /dev/null
+++ b/HASHTAGS
@@ -0,0 +1,15 @@
+# This file is used by the post upload hook in the PRESUBMIT file to
+# automatically change a CL's description based on the specified hashtags.
+# Please see ${bug_number} for more details.

[mtklein, 2015/03/25 12:59:46]

3586 ?

[rmistry, 2015/03/25 17:24:01]

Done.

+#
+# The format of this file is:
+# hashtag_name,mapped_text
+#
+# Here are some examples:
+# * "projectxyz, BUG=skia:123" would convert "#projectxyz" into "BUG=skia:123".
+# * "notry, NOTRY=true" would convert "#notry" into "NOTRY=true".
+
+dummyproject,BUG=skia:2139
+notry,NOTRY=true
+nocommit,COMMIT=false
+try_android_test_n7_d,CQ_INCLUDE_TRYBOTS=client.skia.android:Test-Android-Nexus7-Tegra3-Arm7-Debug

[mtklein, 2015/03/25 12:59:46]

Does piling more than one thing together on the same line work downstream?  E.g.
  floats,BUG=skia:somebug CQ_INCLUDE_TRYBOTS=some-trybot

I guess we could make it work like this?
  floats,BUG=skia:somebug,CQ_INCLUDE_TRYBOTS=some-trybot
where each comma-separated section is included with a new line if not already
present?

Also, just curious, do things like
   CQ_INCLUDE_TRYBOTS=foo
   CQ_INCLUDE_TRYBOTS=bar
compose, and run foo and bar?

[rmistry, 2015/03/25 17:24:01]

SGTM. Done.
I tried this out in https://codereview.chromium.org/1003273008/ and it did not
work.
Multiple BUG lines do work but looks like multiple CQ_INCLUDE_TRYBOTS lines do
not. I took a look at the CQ code and it looked difficult to add support for it
there so I just made a _HandleAppendingCQKeywords function in the PRESUBMIT that
handles this.
Done.