filemerge: use new function for getting first line of string Differential Revision: https://phab.mercurial-scm.org/D12411

absorb: use new function for getting first line of string Differential Revision: https://phab.mercurial-scm.org/D12410

extensions: use new function for getting first line of string Differential Revision: https://phab.mercurial-scm.org/D12409

bookmarks: use new function for getting first line of string Differential Revision: https://phab.mercurial-scm.org/D12408

help: use new function for getting first line of string Differential Revision: https://phab.mercurial-scm.org/D12407

histedit: remove an unnecessary default value of `b''` for commit message I don't think `ctx.description()` is ever anything falsy other than `b''`. I think the comment added in 4c4232e51167 (histedit: extract common summary code into method, 2016-05-27) is mistaken (I don't see any code following that pattern before the function was added). Differential Revision: https://phab.mercurial-scm.org/D12406

histedit: use new function for getting first line of a string This fixes a crash you can run into if you enter a commit message that's just a "newline-like" byte, like a form feed byte (`hg ci -m \x0f` in Fish). That bug is the motivation for this series. Differential Revision: https://phab.mercurial-scm.org/D12405

templates: extract function to `stringutil` for getting first line of text It's surprisingly hard to get the first line from a string, so let's have our own function in `stringutil` for it. Differential Revision: https://phab.mercurial-scm.org/D12404

templates: make `firstline` filter not keep '\v', '\f' and similar In b288b4bb8448 (hide some functions behind lambdas, so demandload is useful., 2006-02-28), `x.splitlines(1)[0]` was replaced by `x.splitlines(1)[0].rstrip('\r\n')`, i.e. stripping trailing '\r' and '\n'. Combined with the "truthy" `1` passed to `splitlines()` to get it to keep line endings, that results in e.g. trailing '\v' (Line Tabulation) and '\f' (Form Feed) being preserved. I can't see why one would want that, and I doubt that was the intention; I suspect the author just didn't think to instead remove the `1` argument. Perhaps they thought the 1 being passed there - added by themselves in a7e416bf3c1d (improve templating., 2006-02-27) - was to limit the number of splits to 1 (i.e. thinking about it as `maxsplit=1` rather than `keepends=1`). Differential Revision: https://phab.mercurial-scm.org/D12403

pytype: drop py3.6 support Pytype 2022.01.07 only supports 3.7+. Differential Revision: https://phab.mercurial-scm.org/D12400