dirstate-v2: Add internal documentation
It can be viewed by running `hg help internals.dirstate-v2`
Since that command rewraps paragraphs, the source text is written with
semantic line breaks: https://sembr.org/
Differential Revision: https://phab.mercurial-scm.org/D11546
BasedOnStyle: LLVM
IndentWidth: 8
UseTab: ForIndentation
BreakBeforeBraces: Linux
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false
AllowShortBlocksOnASingleLine: false
AllowShortFunctionsOnASingleLine: false
IncludeCategories:
- Regex: '^<'
Priority: 1
- Regex: '^"'
Priority: 2