print: beancount: convert underscores in account names to CamelCase

[waj]

Underscore-separated subparts within an account name component are now capitalised and joined, so e.g. assets:wells_fargo:fima_usd becomes Assets:WellsFargo:FimaUsd instead of the previous hex-encoded Assets:WellsC5ffargo:FimaC5fusd. Underscores in hledger account names are conventionally used as a space substitute, so treating them as word boundaries produces much cleaner Beancount output.

[simonmichael]

Thanks for the PR.
We haven't had review bandwidth to keep up with PRs lately; this will be reviewed ASAP.

[simonmichael]

I use hyphens rather than underscores to separate account name sub-parts; and of course spaces are the other common separator. Here's how they're all handled currently:

~/src/hledger$ cat a.j
2000-01-01
  Assets
  Expenses:foo_bar  1
  Expenses:foo-bar  1
  Expenses:foo bar  1

~/src/hledger$ hledger -f a.j print -O beancount
...
2000-01-01 *
    Assets:A
    Expenses:FooC5fbar            1 CC
    Expenses:Foo-bar              1 CC
    Expenses:Foo-bar              1 CC

Would it be simpler and more consistent to replace _ with - ?

https://hledger.org/1.52/hledger.html#beancount-account-names currently says

hledger will adjust your account names to make valid Beancount account names by capitalising each part, replacing spaces with -, replacing other unsupported characters with C<HEXBYTES>, prepending A to account name parts which don't begin with a letter or digit, and appending :A to account names which have only one part.

It would be nice to always use - and never C<HEXBYTES>; but I think we can't do that, because then you could quite easily get names containing many hyphens, likely to overlap.