Re: [PATCH 4/4] mergetools/meld: Use '--output' when available

[Jonathan Nieder <jrnieder@xxxxxxxxx>]

David Aguilar wrote:

> use the '--output' option when available.

Yay. :)

> --- a/mergetools/meld
> +++ b/mergetools/meld
> @@ -4,6 +4,37 @@ diff_cmd () {
>  
>  merge_cmd () {
>  	touch "$BACKUP"
> -	"$merge_tool_path" "$LOCAL" "$MERGED" "$REMOTE"
> +	if test "$meld_has_output_option" = true
> +	then
> +		"$merge_tool_path" --output "$MERGED" \
> +			"$BASE" "$LOCAL" "$REMOTE"

Shouldn't this be "$LOCAL" "$BASE" "$REMOTE"?

> +	else
> +		"$merge_tool_path" "$LOCAL" "$MERGED" "$REMOTE"
> +	fi
>  	check_unchanged

I wonder if the version test could be made a little simpler (perhaps
to cope better if future versions use a different numbering system):

	if "$merge_tool_path" --output /dev/null --help >/dev/null 2>&1
	then
		"$merge_tool_path" --output ...
	else
		"$merge_tool_path" "$LOCAL" ...
	fi

Forgive my ignorance: is this function likely to be called in a loop?
If so, it makes sense to precompute or cache the result of detection,
like you already do.

	check_meld_for_output_option () {
		if ...
		then
			meld_has_output_option=true
		else
			meld_has_output_option=false
		fi
	}

	merge_cmd () {
		if test -z "${meld_has_output_option:+set}"
		then
			check_meld_for_output_option
		fi

		if test "$meld_has_output_option" = true
		then
			...


[...]
> +	# Filter meld --version to contain numbers and dots only
> +	meld="$(meld --version 2>/dev/null | sed -e 's/[^0-9.]\+//g')"

\+ is not a BRE.  If parsing version numbers seems like the right
thing to do, maybe "tr -cd 0-9."?

> +	meld="${meld:-0.0.0}"
> +
> +	meld_major="$(expr "$meld" : '\([0-9]\{1,\}\)' || echo 0)"
> +	meld_minor="$(expr "$meld" : '[0-9]\{1,\}\.\([0-9]\{1,\}\)' || echo 0)"

I think git avoids \{m,n\} ranges where possible (for portability).
This could be:

	meld_major=${meld%%.*}
	meld_nonmajor=${meld#${meld_major}.}
	meld_minor=${meld_nonmajor%%.*}

or:

	case $meld in
	[2-9].* | [1-9][0-9]* | 1.[5-9]* | 1.[1-9][0-9]*)	# >= 1.5.0
		meld_has_output_option=true ;;
	*)
		meld_has_output_option=false ;;
	esac

It's nice how self-contained this can be now that it's in its own
file.  Thanks.
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