hgsh: enable clang-format
Nothing looks awful, so we can just turn it on.
Differential Revision: https://phab.mercurial-scm.org/D2059
BasedOnStyle: LLVM
IndentWidth: 8
UseTab: ForIndentation
BreakBeforeBraces: Linux
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false
AllowShortBlocksOnASingleLine: false
AllowShortFunctionsOnASingleLine: false