Run a program, converting UNIX and Windows format path arguments.

.gitconfig

# Example usage: part of my .gitconfig file (Cygwin git)

[diff]
	tool = winmerge
[difftool "winmerge"]
	cmd = cygrun -w 'C:/Program Files/WinMerge/WinMergeU.exe' -r -u -e -dl \"Local\" -dr \"Remote\" \"$LOCAL\" \"$REMOTE\"
[difftool "diffmerge"]
	cmd = cygrun -w 'C:/Program Files/SourceGear/Common/DiffMerge/sgdm.exe' \"$LOCAL\" \"$REMOTE\"
[difftool]
	prompt = false
[merge]
	tool = winmerge
[mergetool]
	prompt = false
	keepBackup = false
[mergetool "winmerge"]
	trustExitCode = true
	cmd = cygrun -w 'C:/Program Files/WinMerge/WinMergeU.exe' -r -u -e -dl \"Local\" -dr \"Remote\" \"$LOCAL\" \"$REMOTE\" \"$BASE\" \"$MERGED\"
[mergetool "diffmerge"]
	trustExitCode = true
	cmd = cygrun -w 'C:/Program Files/SourceGear/Common/DiffMerge/sgdm.exe' --merge --result=\"$MERGED\" \"$LOCAL\" \"$BASE\" \"$REMOTE\"

cygrun.sh

#!/bin/bash
#
# Run a program, converting UNIX and Windows format path arguments.
#
# Install in Cygwin's `bin` dir or elsewhere in your path. 
# Create a symlink for convenience: `ln -s cygrun.sh cygrun`.
#
# Use `cygrun -w windows-program unix-path ...` to run Windows programs (e.g. from UNIX software).
# E.g., in my .gitconfig core.editor is set to `cygrun -w 'C:/Program Files/Notepad2/Notepad2.exe'`.
#
# Use `cygrun [-u] unix-program windows-path ...` to run Cygwin programs (e.g. from Windows software).
# Usually not needed since Cygwin translates Windows paths automatically (e.g. `ls 'C:\Windows'` works).
# Still it can be useful in case a Windows program might produce paths that mix backslashes and forward slashes,
# e.g. in Apache Ant `${dist.dir}/file` evaluates to `C:\path\to\project\dist/file`, which Cygwin won't
# translate automatically. So, to deploy the file, I use `cygrun -u scp ${dist.dir}/file ${deploy.url}`.
#
# Use the `-b` option to detach from tty, run the process in background, and return immediately.
#
# There is currently a limitation on passing non-path arguments to a program. Since there is no way
# to automatically distinguish path arguments from non-path arguments, all of the arguments are passed
# to `cygpath`. As long as non-path arguments don't contain `/` or `\` characters, and `-a` or `-C`
# options are not used, `cygpath` will return the arguments unmodified - no problem.
# Due to this, the `-a` and `-C` options are disabled at the moment.
# TODO: Add an option allowing to specify index positions of path arguments (comma-separated, support ranges).
#
# Most of the options are passed as is to `cygpath`, which is used for path conversion.

set -e -o pipefail

usage() {
	local code=${1:-2}
	test $code -ne 0 && exec >&2
	
	echo "Usage: $(basename "$0" .sh) [options] program [argument]..."
	echo
	echo 'Run a program, converting UNIX and Windows format path arguments.'
	echo
	echo 'Output type options:'
	echo
	echo '  -d, --dos             print DOS (short) form of NAMEs (C:\PROGRA~1\)'
	echo '  -m, --mixed           like --windows, but with regular slashes (C:/WINNT)'
	echo '  -u, --unix            (default) print Unix form of NAMEs (/cygdrive/c/winnt)'
	echo '  -w, --windows         print Windows form of NAMEs (C:\WINNT)'
	echo
	echo 'Path conversion options:' 
	echo
#	echo '  -a, --absolute        output absolute path'
	echo '  -U, --proc-cygdrive   Emit /proc/cygdrive path instead of cygdrive prefix'
	echo '                        when converting Windows path to UNIX path.'
	echo '  -c, --codepage CP     print DOS, Windows, or mixed pathname in Windows'
	echo '                        codepage CP.  CP can be a numeric codepage identifier,'
	echo '                        or one of the reserved words ANSI, OEM, or UTF8.'
	echo '                        If this option is missing, cygrun defaults to the'
	echo '                        character set defined by the current locale.'
	echo
	echo "Other 'cygpath' options:"
	echo
	echo '  -f, --file FILE       read FILE for input; use - to read from STDIN'
	echo "  -o, --option          read 'cygpath' options from FILE as well (for use with --file)"
	echo '  -h, --help            output usage information and exit'
	echo
	echo 'Run options:'
	echo
#	echo '  -c, --directory DIR   change to directory DIR (implies -a)'
	echo '  -b, --background      run in a new session'
	echo '  -n, --dry-run         print the command that would be executed, and exit'
	
	exit $code
}

run() {
	local -n _run_args=$2
	if test "$dry_run"; then
		test "$chdir" && printf 'cd %s\n' "$chdir"
		printf '%s\n' "$1 ${_run_args[*]}"
	else
		test "$chdir" && cd -- "$chdir"
		#printf '[debug] %s\n' "$1 ${_run_args[*]}" >&2 # DEBUG
		if test "$background"; then
			setsid "$1" "${_run_args[@]}" </dev/null &>/dev/null &
		else
			exec "$1" "${_run_args[@]}"
		fi
	fi
}

declare opts fileopts chdir background dry_run
while test $# -gt 0; do
	case $1 in
#		-d|--dos|-u|--unix|-m|--mixed|-w|--windows|-a|--absolute|-U|--proc-cygdrive|-o|--option)
		-d|--dos|-u|--unix|-m|--mixed|-w|--windows|-U|--proc-cygdrive|-o|--option)
			opts="${opts} $1"
		;;
		-C|--codepage|-f|--file)
			opts="${opts} $1 $2"
			shift
		;;
		-f|--file)
			fileopts=1
			opts="${opts} -i $1 $2"
			shift
		;;
#		-c|--directory)
#			shift
#			chdir=$1
#		;;
		-b|--background)
			background=1
		;;
		-n|--dry-run)
			dry_run=1
		;;
		-h|--help)
			usage 0
		;;
		--)
			shift
			break
		;;
		-*)
			script="$(basename "$0" .sh)"
			echo "$script: Unknown option: $1" >&2
			echo "Try '$script --help' for more information." >&2
			exit 2
		;;
		*)
			break
		;;
	esac
	shift
done
test "$chdir" && opts="$opts -a"

program=$1
test "$program" || usage
shift

declare -a args
#test $# -gt 0 -o "$fileopts" && echo '[debug]' mapfile -t args \< \<\(cygpath $opts -- \""$@"\" \|\| exit 1\) >&2 # DEBUG 
test $# -gt 0 -o "$fileopts" && mapfile -t args < <(cygpath $opts -- "$@" || exit 1)
run "$program" args