branch: operate on branch names in local string space where possible Previously, branch names were ideally manipulated as UTF-8 strings, because they were stored as UTF-8 in the dirstate and the changelog and could not be safely converted to the local encoding and back. However, only about 80% of branch name code was actually using the right encoding conventions. This patch uses the localstr addition to allow working on branch names as local strings, which simplifies handling so that the previously incorrect code becomes correct.