fix parsing of tags. make parse errors useful. add new tag tests. old code read every head of .hgtags. delete and recreate of .hgtags gave new head, but if error in deleted rev, .hgtags had error messages every time it was parsed. this was very hard to fix, because deleted revs hard to get back and update, needed merges too. new code reads .hgtags on every head. advantage is if parse error happens with new code, is possible to fix them by editing .hgtags on a head and committing. NOTE: new code uses binary search of manifest of each head to be fast, but still much slower than old code. best thing would be to have delete record stored in filelog so we never touch manifest. could find live heads directly from filelog. this is more work than i want now. new tests check for parse of tags on different heads, and inaccessible heads created by delete and recreate of .hgtags.

1:f248da0d4c3e
0:9eca13a34789
f248da0d4c3e tip
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
9eca13a34789
9eca13a34789+
reverting file1
9eca13a34789
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
f248da0d4c3e tip
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
merge: warning: conflicts during merge
merging file1
merging file1 failed!
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
There are unresolved merges with locally modified files.
diff -r f248da0d4c3e file1
--- a/file1
+++ b/file1
@@ -1,3 +1,7 @@ added file1
 added file1
 another line of text
+<<<<<<<
+changed file1 different
+=======
 changed file1
+>>>>>>>
M file1
f248da0d4c3e+ tip
reverting file1
f248da0d4c3e tip
f248da0d4c3e tip
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
f248da0d4c3e tip