Merge branch 'ab/doc-synopsis-and-cmd-usage'

Merge branch 'ab/doc-synopsis-and-cmd-usage'

The short-help text shown by "git cmd -h" and the synopsis text
shown at the beginning of "git help cmd" have been made more
consistent.

* ab/doc-synopsis-and-cmd-usage: (34 commits)
  tests: assert consistent whitespace in -h output
  tests: start asserting that *.txt SYNOPSIS matches -h output
  doc txt & -h consistency: make "worktree" consistent
  worktree: define subcommand -h in terms of command -h
  reflog doc: list real subcommands up-front
  doc txt & -h consistency: make "commit" consistent
  doc txt & -h consistency: make "diff-tree" consistent
  doc txt & -h consistency: use "[<label>...]" for "zero or more"
  doc txt & -h consistency: make "annotate" consistent
  doc txt & -h consistency: make "stash" consistent
  doc txt & -h consistency: add missing options
  doc txt & -h consistency: use "git foo" form, not "git-foo"
  doc txt & -h consistency: make "bundle" consistent
  doc txt & -h consistency: make "read-tree" consistent
  doc txt & -h consistency: make "rerere" consistent
  doc txt & -h consistency: add missing options and labels
  doc txt & -h consistency: make output order consistent
  doc txt & -h consistency: add or fix optional "--" syntax
  doc txt & -h consistency: fix mismatching labels
  doc SYNOPSIS & -h: use "-" to separate words in labels, not "_"
  ...