Re: [PATCH 1/3] mergetool-lib: use $XDG_CURRENT_DESKTOP to check GNOME

[Eric Sunshine <sunshine@sunshineco.com>]

On Wed, Aug 5, 2020 at 3:51 PM Marco Trevisan (Treviño) via
GitGitGadget <gitgitgadget@gmail.com> wrote:
> To list merge tool candidates we used to use a private GNOME env
> variable (GNOME_DESKTOP_SESSION_ID) that has been deprecated for long time ago
> and removed as part of GNOME 3.30.0 release [1].
>
> So, git should instead check the XDG_CURRENT_DESKTOP env variable, that
> is supported by all the desktop environments.
>
> Since the variable is actually a colon-separated list of names that the current
> desktop is known as, we need to go through all the values to ensure
> we're using GNOME.
>
> Signed-off-by: Marco Trevisan (Treviño) <mail@3v1n0.net>
> ---
> diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
> @@ -266,6 +266,19 @@ run_merge_cmd () {
> +is_desktop () {
> +       IFS=':'

We usually want to restore the value of IFS after we're done with it.
For instance:

    OLDIFS=$IFS
    IFS=:

and then restore it before returning:

    IFS=$OLDIFS

> +       for desktop in ${XDG_CURRENT_DESKTOP}
> +       do
> +               if test "$desktop" = "$1"
> +               then
> +                       return 0
> +               fi
> +       done
> +
> +       return 1
> +}

Rather than looping and mucking with IFS, even easier would be:

is_desktop () {
    case ":$XDG_CURRENT_DESKTOP:" in
    *:$1:*) return 0 ;;
    *) return 1 ;;
    esac
}

But perhaps that's too magical for people?

> @@ -275,7 +288,7 @@ list_merge_tool_candidates () {
> -               if test -n "$GNOME_DESKTOP_SESSION_ID"
> +               if is_desktop "GNOME"

Why do we need to retire the $GNOME_DESKTOP_SESSION_ID check here,
thus penalizing people who might still be on an old version of GNOME?
It doesn't seem like it would be a maintenance burden to continue
checking it while also taking advantage of $XDG_CURRENT_DESKTOP:

    if test -n "$GNOME_DESKTOP_SESSION_ID" || is_desktop GNOME