[PATCH v3 0/8] git-prompt: support more shells v3

This addresses review comments on part 5/8 v2 (git-prompt: add some missing quotes) to fix typo in the commit message "aguments" into "arguments", but which was used to reword it a bit so that it's more accurate.

Also addresses review comment on part 7/8 v2 (git-prompt: ta-da! document usage in other shells) and fix typo "Conpatibility".

Avi Halachmi (:avih) (8):
  git-prompt: use here-doc instead of here-string
  git-prompt: fix uninitialized variable
  git-prompt: don't use shell arrays
  git-prompt: replace [[...]] with standard code
  git-prompt: add some missing quotes
  git-prompt: don't use shell $'...'
  git-prompt: ta-da! document usage in other shells
  git-prompt: support custom 0-width PS1 markers

 contrib/completion/git-prompt.sh | 191 ++++++++++++++++++++-----------
 1 file changed, 126 insertions(+), 65 deletions(-)

base-commit: d19b6cd2dd72dc811f19df4b32c7ed223256c3ee
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1750%2Favih%2Fprompt-compat-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1750/avih/prompt-compat-v3
Pull-Request: https://github.com/git/git/pull/1750

Range-diff vs v2:

 1:  9ce5ddadf0b = 1:  9ce5ddadf0b git-prompt: use here-doc instead of here-string
 2:  680ecb52404 = 2:  680ecb52404 git-prompt: fix uninitialized variable
 3:  7e994eae7bc = 3:  7e994eae7bc git-prompt: don't use shell arrays
 4:  232340902a1 = 4:  232340902a1 git-prompt: replace [[...]] with standard code
 5:  4f77b7eb7f1 ! 5:  3a41ad889cc git-prompt: add some missing quotes
     @@ Commit message
            not expanded:   t="~"; a=${t}user  b=\~foo~;  echo "~user" $t/dir
      
          But the main reason for quoting is to prevent IFS field splitting
     -    (which also coalesces IFS chars) and glob expansion after parameter
     -    expansion or command substitution.
     +    (which also coalesces IFS chars) and glob expansion in parts which
     +    contain parameter/arithmetic expansion or command substitution.
      
     -    In _command-arguments_, expanded/substituted values must be quoted:
     +    "Simple command" (POSIX term) is assignment[s] and/or command [args].
     +    Examples:
     +      foo=bar         # one assignment
     +      foo=$bar x=y    # two assignments
     +      foo bar         # command, no assignments
     +      x=123 foo bar   # one assignment and a command
     +
     +    The assignments part is not IFS-split or glob-expanded.
     +
     +    The command+args part does get IFS field split and glob expanded,
     +    but only at unquoted expanded/substituted parts.
     +
     +    In the command+args part, expanded/substituted values must be quoted.
     +    (the commands here are "[" and "local"):
            Good: [ "$mode" = yes ]; local s="*" x="$y" e="$?" z="$(cmd ...)"
            Bad:  [ $mode = yes ];   local s=*   x=$y   e=$?   z=$(cmd...)
      
     -    Still in _agumemts_, no need to quote non-expandable values:
     +    The arguments to "local" do look like assignments, but they're not
     +    the assignment part of a simple command. they're at the command part.
     +
     +    Still at the command part, no need to quote non-expandable values:
            Good:                 local x=   y=yes;   echo OK
            OK, but not required: local x="" y="yes"; echo "OK"
          But completely empty (NULL) arguments must be quoted:
     @@ Commit message
          "local" does not behave with assignment context in some shells,
          hence we require quotes when using "local" - for compatibility.
      
     -    First value in 'case...' doesn't IFS-split/glob, doesn't need quotes:
     +    The value between 'case' and 'in' doesn't IFS-split/glob-expand:
            Good:       case  * $foo $(cmd...)  in ... ; esac
            identical:  case "* $foo $(cmd...)" in ... ; esac
      
 6:  363b7015763 = 6:  e735a1696a0 git-prompt: don't use shell $'...'
 7:  4aa75cdb5dd ! 7:  e70440e669a git-prompt: ta-da! document usage in other shells
     @@ contrib/completion/git-prompt.sh
       # GIT_PS1_HIDE_IF_PWD_IGNORED to a nonempty value. Override this on the
       # repository level by setting bash.hideIfPwdIgnored to "false".
      +#
     -+# Conpatibility with other shells (beyond bash/zsh):
     ++# Compatibility with other shells (beyond bash/zsh):
      +#
      +#    We require posix-ish shell plus "local" support, which is most
      +#    shells (even pdksh), but excluding ksh93 (because no "local").
 8:  e71ddcd2232 = 8:  633e71a01d3 git-prompt: support custom 0-width PS1 markers