Merge branch 'pb/subtree-split-and-merge-after-squashing-tag-fix'
A bugfix to "git subtree" in its split and merge features.
* pb/subtree-split-and-merge-after-squashing-tag-fix:
subtree: fix split after annotated tag was squashed merged
subtree: fix squash merging after annotated tag was squashed merged
subtree: process 'git-subtree-split' trailer in separate function
subtree: use named variables instead of "$@" in cmd_pull
subtree: define a variable before its first use in 'find_latest_squash'
subtree: prefix die messages with 'fatal'
subtree: add 'die_incompatible_opt' function to reduce duplication
subtree: use 'git rev-parse --verify [--quiet]' for better error messages
test-lib-functions: mark 'test_commit' variables as 'local'