crecord: add `content` properties to all nodes
In order to have a unified API of what can be searched, let's provide
a `content` property to each node type. This way we can search
filenames, context headers (e.g. containing function names, if
deducible from patch context) or changed lines themselves.
$ hg init repo
$ cd repo
$ echo a > a
$ hg ci -Am t
adding a
$ hg mv a b
$ hg ci -Am t1
$ hg debugrename b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3
$ hg mv b a
$ hg ci -Am t2
$ hg debugrename a
a renamed from b:37d9b5d994eab34eda9c16b195ace52c7b129980
$ hg debugrename --rev 1 b
b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3