ui: move protectedstdio() context manager from procutil This is a follow-up series for 23a00bc90a3c, "chgserver: do not send system() back to client if stdio redirected." The function is renamed using ui terms.

cext: clang-format new code coming from stable branch

match: support rooted globs in hgignore In a .hgignore, "glob:foo" always means "**/foo". This cannot be avoided because there is no syntax like "^" in regexes to say you don't want the implied "**/" (of course one can use regexes, but glob syntax is nice). When you have a long list of fairly specific globs like path/to/some/thing, this has two consequences: 1. unintended files may be ignored (not too common though) 2. matching performance can suffer significantly Here is vanilla hg status timing on a private repository: Using syntax:glob everywhere real 0m2.199s user 0m1.545s sys 0m0.619s When rooting the appropriate globs real 0m1.434s user 0m0.847s sys 0m0.565s (tangentially, none of this shows up in --profile's output. It seems that C code doesn't play well with profiling) The code already supports this but there is no syntax to make use of it, so it seems reasonable to create such syntax. I create a new hgignore syntax "rootglob". Differential Revision: https://phab.mercurial-scm.org/D5493