help: teach topic symbols how to dedent When using docstrings for documenting symbols such as revsets, templates, or hgweb commands, documentation likely has leading whitespace corresponding to the indentation from the Python source file. Up until this point, the help system stripped all leading and trailing whitespace and replaced it with 2 spaces of leading whitespace. There were a few bad side-effects. First, sections could not be used in docstrings because they would be indented and the rst parser would fail to parse them as sections. Also, any rst elements that required indentation would lose their indentation, again causing them to be parsed and rendered incorrectly. In this patch, we teach the topic symbols system how to dedent text properly. I argue this mode should be enabled by default. However, I stopped short of changing that because it would cause a lot of documentation reformatting to occur. I'm not sure if people are relying on or wanting indentation. So, dedenting has only been turned on for hgweb symbols. This decision should be scrutinized.