debugcommands: support wrapping long lines If a line within a block is indented more than the line that came before, we automatically concatenate it with the previous line. This allows us to pretty format data. This will make tests easier to read. At some point we may just want to evaluate entire blocks as Python code or something, as even with this change, things aren't perfect, as we can't e.g. have formatting like: foo eval:[ True ] But this is strictly better than before, where we couldn't wrap long lines. Differential Revision: https://phab.mercurial-scm.org/D4977