Merge branch 'jk/maint-status-porcelain-z-b' into maint

"git status --porcelain" ignored "--branch" option by mistake.  The output
for "git status --branch -z" was also incorrect and did not terminate the
record for the current branch name with NUL as asked.

By Jeff King
* jk/maint-status-porcelain-z-b:
status: respect "-b" for porcelain format
status: fix null termination with "-b"
status: refactor null_termination option
commit: refactor option parsing

diff --combined Documentation/git-status.txt
index a29aae60cded28263785b3f35640246837b0df30,16ae5c3f27fdde4c1dd99d301c6ec166d2507ab8..277e1e2ca31f1b3a8d5a32d9955ff22ecd82ec37
--- 1/Documentation/git-status.txt
--- 2/Documentation/git-status.txt
+++ b/Documentation/git-status.txt
@@@ -98,12 -98,12 +98,12 @@@ In the short-format, the status of eac
  
        XY PATH1 -> PATH2
  
 -where `PATH1` is the path in the `HEAD`, and the ` \-> PATH2` part is
 +where `PATH1` is the path in the `HEAD`, and the " `-> PATH2`" part is
  shown only when `PATH1` corresponds to a different path in the
  index/worktree (i.e. the file is renamed). The 'XY' is a two-letter
  status code.
  
 -The fields (including the `\->`) are separated from each other by a
 +The fields (including the `->`) are separated from each other by a
  single space. If a filename contains whitespace or other nonprintable
  characters, that field will be quoted in the manner of a C string
  literal: surrounded by ASCII double quote (34) characters, and with
@@@ -177,7 -177,7 +177,7 @@@ order is reversed (e.g 'from \-> to' be
  and the terminating newline (but a space still separates the status
  field from the first filename).  Third, filenames containing special
  characters are not specially formatted; no quoting or
- backslash-escaping is performed. Fourth, there is no branch line.
+ backslash-escaping is performed.
  
  CONFIGURATION
  -------------