mozautomation: match built URIs exactly in resolve_uri_to_tree (Bug…

… 1768982) r=zeid

`resolve_uri_to_tree` takes a URI (ie `https://hg.mozilla.org/mozilla-central`)
and attempts to resolve it to a known Firefox tree shortname (ie `central`).
It does so by iterating through the list of known Firefox tree repo names and
building out each potential URI, and then checking if each built URI matches
the passed URI. The matching condition used is `uri.startswith`, assumedly
so something like `https://hg.mozilla.org/mozilla-centra` or some other minor
typo results in a match still being found. This has worked without any issue to
date, until `esr102` was created. Since the built URIs for esr10 would match
the `startswith` metric on `esr102`, passing the URI for esr102 is returning
`esr10` as the resolved tree.

Switch `resolve_uri_to_tree` to return the resolved tree only when the built
URI exactly matches the passed URI. Add a few comments clarifying what the
function is doing and use more descriptive variable names.

Differential Revision: https://phabricator.services.mozilla.com/D146210

--HG--
extra : moz-landing-system : lando

pylib/mozautomation/mozautomation/repository.py

@@ -241,17 +241,24 @@ def resolve_trees_to_uris(trees, write_access=False):
 
 def resolve_uri_to_tree(uri):
     """Try to resolve a URI back to a known tree."""
+    # Account for a trailing `/`.
+    if uri.endswith(b'/'):
+        uri = uri[:-1]
 
     for tree, path in REPOS.items():
-        if uri.startswith(b'%s%s' % (BASE_READ_URI, path)):
+        # Try `https` URI first.
+        read_url_https = b'%s%s' % (BASE_READ_URI, path)
+        if uri == read_url_https:
             return tree
 
-        if uri.startswith(b'%s%s' % (
-            BASE_READ_URI.replace(b'https://', b'http://'),
-            path)):
+        # Try `http` URI next.
+        read_url_http = read_url_https.replace(b'https://', b'http://')
+        if uri == read_url_http:
             return tree
 
-        if uri.startswith(b'%s%s' % (BASE_WRITE_URI, path)):
+        # Try `ssh` URI last.
+        write_url_ssh = b'%s%s' % (BASE_WRITE_URI, path)
+        if uri == write_url_ssh:
             return tree
 
     return None