Parse homu state out of comments

For some critical comments, Homu adds extra information about its state
in the form of a JSON blob to the comment that isn't visible to the user
but is visible in the source for the comment. For example, Homu may
leave a comment like the following, where the JSON blob is not visible
because of the `<!-- .. -->` markdown/html comments.

    ⌛ Trying commit abcdef with merge 012345...

    <!-- homu: {"type":"TryBuildStarted","head_sha":"abcdef","merge_sha":"012345"} -->

This change parses this extra information out of the comments and makes
it available to the initial synchronization algorithm.

homu/parse_issue_comment.py

@@ -1,5 +1,6 @@
 from itertools import chain
 import re
+import json
 
 from .consts import WORDS_TO_ROLLUP
 
@@ -94,6 +95,12 @@ def hook(cls, hook_name, hook_extra=None):
         command.hook_extra = hook_extra
         return command
 
+    @classmethod
+    def homu_state(cls, state):
+        command = cls('homu-state')
+        command.homu_state = state
+        return command
+
 
 def is_sha(sha):
     """
@@ -144,10 +151,17 @@ def parse_issue_comment(username, body, sha, botname, hooks=[]):
            E.g. `['hook1', 'hook2', 'hook3']`
     """
 
-    words = list(chain.from_iterable(re.findall(r'\S+', x) for x in body.splitlines() if '@' + botname in x))  # noqa
-
     commands = []
 
+    states = chain.from_iterable(re.findall(r'<!-- homu:(.*?)-->', x)
+                                 for x
+                                 in body.splitlines())
+
+    for state in states:
+        commands.append(IssueCommentCommand.homu_state(json.loads(state)))
+
+    words = list(chain.from_iterable(re.findall(r'\S+', x) for x in body.splitlines() if '@' + botname in x))  # noqa
+
     if words[1:] == ["are", "you", "still", "there?"]:
         commands.append(IssueCommentCommand.ping('portal'))
 

homu/tests/test_parse_issue_comment.py

@@ -528,3 +528,26 @@ def test_ignore_commands_after_bors_line():
     command = commands[0]
     assert command.action == 'approve'
     assert command.actor == 'jack'
+
+
+def test_homu_state():
+    """
+    Test that when a comment has a Homu state in it, we return that state.
+    """
+
+    author = "bors"
+    body = """
+    :hourglass: Trying commit 3d67c2da893aed40bc36b6ac9148c593aa0a868a with merge b7a0ff78ba2ba0b3f5e1a8e89464a84dc386aa81...
+    <!-- homu: {"type":"TryBuildStarted","head_sha":"3d67c2da893aed40bc36b6ac9148c593aa0a868a","merge_sha":"b7a0ff78ba2ba0b3f5e1a8e89464a84dc386aa81"} -->
+    """ # noqa
+
+    commands = parse_issue_comment(author, body, commit, "bors")
+
+    assert len(commands) == 1
+    command = commands[0]
+    assert command.action == 'homu-state'
+    assert command.homu_state == {
+        'type': 'TryBuildStarted',
+        'head_sha': '3d67c2da893aed40bc36b6ac9148c593aa0a868a',
+        'merge_sha': 'b7a0ff78ba2ba0b3f5e1a8e89464a84dc386aa81',
+    }