sslutil: print the fingerprint from the last hash used

Before, we would always print the unprefixed SHA-1 fingerprint when
fingerprint comparison failed. Now, we print the fingerprint of the
last hash used, including the prefix if necessary. This helps ensure
that the printed hash type matches what is in the user configuration.

There are still some cases where this can print a mismatched hash type.
e.g. if there are both SHA-1 and SHA-256 fingerprints in the config,
we could print a SHA-1 hash if it comes after the SHA-256 hash. But
I'm inclined to ignore this edge case.

While I was here, the "section" variable assignment has been moved to
just above where it is used because it is now only needed for this
error message and it makes the code easier to read.

mercurial/sslutil.py

@@ -377,14 +377,8 b' def validatesocket(sock):'
     def fmtfingerprint(s):
         return ':'.join([s[x:x + 2] for x in range(0, len(s), 2)])
 
-    legacyfingerprint = fmtfingerprint(peerfingerprints['sha1'])
     nicefingerprint = 'sha256:%s' % fmtfingerprint(peerfingerprints['sha256'])
 
-    if settings['legacyfingerprint']:
-        section = 'hostfingerprint'
-    else:
-        section = 'hostsecurity'
-
     if settings['certfingerprints']:
         for hash, fingerprint in settings['certfingerprints']:
             if peerfingerprints[hash].lower() == fingerprint:
@@ -392,8 +386,15 b' def validatesocket(sock):'
                          (host, hash, fmtfingerprint(fingerprint)))
                 return
 
+        # Pinned fingerprint didn't match. This is a fatal error.
+        if settings['legacyfingerprint']:
+            section = 'hostfingerprint'
+            nice = fmtfingerprint(peerfingerprints['sha1'])
+        else:
+            section = 'hostsecurity'
+            nice = '%s:%s' % (hash, fmtfingerprint(peerfingerprints[hash]))
         raise error.Abort(_('certificate for %s has unexpected '
-                            'fingerprint %s') % (host, legacyfingerprint),
+                            'fingerprint %s') % (host, nice),
                           hint=_('check %s configuration') % section)
 
     if not sock._hgstate['caloaded']:

tests/test-https.t

@@ -314,7 +314,7 b' Fingerprints'
   [255]
 
   $ hg --config 'hostsecurity.localhost:fingerprints=sha1:deadbeefdeadbeefdeadbeefdeadbeefdeadbeef, sha1:aeadbeefdeadbeefdeadbeefdeadbeefdeadbeef' -R copy-pull id https://localhost:$HGPORT/
-  abort: certificate for localhost has unexpected fingerprint 91:4f:1a:ff:87:24:9c:09:b6:85:9b:88:b1:90:6d:30:75:64:91:ca
+  abort: certificate for localhost has unexpected fingerprint sha1:91:4f:1a:ff:87:24:9c:09:b6:85:9b:88:b1:90:6d:30:75:64:91:ca
   (check hostsecurity configuration)
   [255]