Merge branch 'jk/interpret-branch-name-fix'

Fix a handful of bugs around interpreting $branch@{upstream} notation and its lookalike, when $branch part has interesting characters, e.g. "@", and ":". * jk/interpret-branch-name-fix: interpret_branch_name: find all possible @-marks interpret_branch_name: avoid @{upstream} past colon interpret_branch_name: always respect "namelen" parameter interpret_branch_name: rename "cp" variable to "at" interpret_branch_name: factor out upstream handling