Fix: harden utimes, use single quotes

[rasa]

EDIT: I replaced the double quotes with single quotes to stop bash from processing shell meta-characters, such as $ and ` in filenames.

EDIT: I also removed passing --posix to bash, as bash may whine about non-posix code in the user's existing environment. For example, if a user has a function name with a colon in it, bash will complain:
bash: line 4: BASH_FUNC_lib:funcname%%': not a valid identifier
when --posix is passed.

Now works on repos with tricky filenames:

$ git-utimes 
+ touch -h -d@1699829680 "`whoami`"
+ touch -h -d@1699829626 "$USER"
+ touch -h -d@1699829626 $USER
+ touch -h -d@1699829337 "'quotes-and-single-quotes'"
+ touch -h -d@1699829337 '"single-quotes-and-quotes"'
+ touch -h -d@1699829337 a-quote-and-single-quote"'
+ touch -h -d@1699829337 a-single-quote-and-quote'"
+ touch -h -d@1699828363 `whoami`
+ touch -h -d@1699828215 file-in-root-dir.symlink
+ touch -h -d@1699828203 root-dir.symlink
+ touch -h -d@1699828037 file-in-dir.symlink
+ touch -h -d@1699827933  a-space-at-the-beginning
+ touch -h -d@1699720671 "2-quotes"
+ touch -h -d@1699720671 '2-single-quotes'
+ touch -h -d@1699720671 2-quotes-together""
+ touch -h -d@1699720671 2-single-quotes-together''
+ touch -h -d@1699720671 a-single-quote'
+ touch -h -d@1675048802 a-colon:
+ touch -h -d@1627401449 a-backslash\
+ touch -h -d@1627399934 CON.txt
+ touch -h -d@1627399912 CON
+ touch -h -d@1626789305 a-space
+ touch -h -d@1626789277 a-dot.
+ touch -h -d@1626789249 a-less-than<
+ touch -h -d@1626789223 a-greater-than>
+ touch -h -d@1626789196 a-pipe|
+ touch -h -d@1626789165 a-question-mark?
+ touch -h -d@1626789137 a-asterisk*
+ touch -h -d@1626789107 a-quote"
+ touch -h -d@1619369190 executable.sh
+ touch -h -d@1608172298 executable.cmd
+ touch -h -d@1607657114 CASESENSITIVE.TXT
+ touch -h -d@1607656480 CaseSensitive.txt
+ touch -h -d@1607656480 casesensitive.txt
+ touch -h -d@1607651028 file☠☡☢☣.txt
+ touch -h -d@1607650377 dir.symlink
+ touch -h -d@1607650377 dir/file
+ touch -h -d@1607650181 file
+ touch -h -d@1607650181 file.symlink
+ touch -h -d@1607649124 .gitignore
+ touch -h -d@1607649124 LICENSE
+ touch -h -d@1607649124 README.md
$ ls -al
total 108
drwxr-xr-x  4 ross ross 4096 Nov 12 15:06  .
drwxr-xr-x 30 ross ross 4096 Nov 12 15:06  ..
drwxr-xr-x  2 ross ross 4096 Nov 12 15:06  dir
lrwxrwxrwx  1 ross ross    3 Dec 10  2020  dir.symlink -> dir
lrwxrwxrwx  1 ross ross    6 Nov 12 14:30  root-dir.symlink -> dir/..
-rw-r--r--  1 ross ross    0 Nov 12 14:53 '"$USER"'
-rw-r--r--  1 ross ross    0 Nov 12 14:53 '$USER'
-rw-r--r--  1 ross ross    0 Nov 11 08:37 '"2-quotes"'
-rw-r--r--  1 ross ross    0 Nov 11 08:37 '2-quotes-together""'
-rw-r--r--  1 ross ross    0 Nov 11 08:37 "'2-single-quotes'"
-rw-r--r--  1 ross ross    0 Nov 11 08:37 "2-single-quotes-together''"
-rw-r--r--  1 ross ross   12 Jul 20  2021 'a-asterisk*'
-rw-r--r--  1 ross ross   13 Nov 12 15:06 'a-backslash\'
-rw-r--r--  1 ross ross    9 Jan 29  2023  a-colon:
-rw-r--r--  1 ross ross    1 Jul 20  2021  a-dot.
-rw-r--r--  1 ross ross   16 Jul 20  2021 'a-greater-than>'
-rw-r--r--  1 ross ross   13 Jul 20  2021 'a-less-than<'
-rw-r--r--  1 ross ross    8 Jul 20  2021 'a-pipe|'
-rw-r--r--  1 ross ross   17 Jul 20  2021 'a-question-mark?'
-rw-r--r--  1 ross ross    9 Jul 20  2021 'a-quote"'
-rw-r--r--  1 ross ross    0 Nov 12 14:48 'a-quote-and-single-quote"'\'''
-rw-r--r--  1 ross ross    0 Nov 11 08:37 "a-single-quote'"
-rw-r--r--  1 ross ross    0 Nov 12 14:48 'a-single-quote-and-quote'\''"'
-rw-r--r--  1 ross ross    9 Jul 20  2021  a-space
-rw-r--r--  1 ross ross    0 Nov 12 14:25 ' a-space-at-the-beginning'
-rw-r--r--  1 ross ross   18 Dec 10  2020  casesensitive.txt
-rw-r--r--  1 ross ross   18 Dec 10  2020  CaseSensitive.txt
-rw-r--r--  1 ross ross   19 Dec 10  2020  CASESENSITIVE.TXT
-rw-r--r--  1 ross ross    4 Jul 27  2021  CON
-rw-r--r--  1 ross ross    8 Jul 27  2021  CON.txt
-rwxr-xr-x  1 ross ross   20 Dec 16  2020  executable.cmd
-rwxr-xr-x  1 ross ross   42 Apr 25  2021  executable.sh
-rw-r--r--  1 ross ross    5 Dec 10  2020  file
lrwxrwxrwx  1 ross ross    8 Nov 12 14:27  file-in-dir.symlink -> dir/file
lrwxrwxrwx  1 ross ross   11 Nov 12 14:30  file-in-root-dir.symlink -> dir/../file
lrwxrwxrwx  1 ross ross    4 Dec 10  2020  file.symlink -> file
-rw-r--r--  1 ross ross   21 Dec 10  2020  file☠☡☢☣.txt
-rw-r--r--  1 ross ross 1799 Dec 10  2020  .gitignore
-rw-r--r--  1 ross ross 1070 Dec 10  2020  LICENSE
-rw-r--r--  1 ross ross    0 Nov 12 14:48 '"'\''quotes-and-single-quotes'\''"'
-rw-r--r--  1 ross ross   54 Dec 10  2020  README.md
-rw-r--r--  1 ross ross    0 Nov 12 14:48 ''\''"single-quotes-and-quotes"'\'''
-rw-r--r--  1 ross ross    0 Nov 12 14:54 '"`whoami`"'
-rw-r--r--  1 ross ross    9 Nov 12 14:32 '`whoami`'

[hyperupcall]

thanks! i just had one question and then you'll get an okay from me