Fixed indentation including issues with "=" normal mode command.

[bak-t]

These changes should fix issue #27. I replaced smartindent with fine tuned cindent.

[heaths]

Thank you for the PR! I'm doing some manual testing, and found automatic one-space indentation in the following scenario:

Without your changes, everything stays on the previous line's column. Reading about these cindent-related options - which I admit in 30 some years I haven't really played with much - it seems may be related to the cinkeys options.

Thoughts? I tried to think and test a bunch of indent-related tasks and, for the most part, this does seem to work better, like auto-indenting parameters in a param() block.

[bak-t]

I was able to slightly improve indentation of comments with > normal mode command (for comment started from 1st column only 1 space is used instead of shiftwidth).
But the bug you've found in insert mode still persists. I'll try to experiment with cinkeys.

[heaths]

Thanks. I look forward to it. I think this is a big step in the right direction, but worry if I found an arguably minor regression, what other possibly larger regressions have I missed? Hopefully whatever could resolve this issue would mitigate at least some risk of regression elsewhere.

[bak-t]

It seems that cinkeys doesn't help with the issue found or at least I'm unable to find proper values for it.
Also I found that with current fix = normal mode command changes indentation of comments back & forth at root scope at each run. For example:

# comment
# another comment
  # mistakenly indented comment

after gg=G looks like:

  # comment
  # another comment
# mistakenly indented comment

after .:

# comment
# another comment
  # mistakenly indented comment

and so on.

I'll experiment with indentexpr. Looks like it's possible to combine it with C-indent by using cindent function. So, solution may be perform handcrafted indentation for edge cases & call cindent function otherwise. This also could make possible to skip indentation in here-strings.