Set COLORTERM variable to advertise 24-bit support

Set `COLORTERM` to `truecolor` in order for applications to be able to
detect that alacritty supports 24-bit colors.

See https://gist.github.com/XVilka/8346728 for more details.

Closes #1526.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/tty.rs b/src/tty.rs
index 4da11c0e..9f6a2e64 100644
--- a/src/tty.rs
+++ b/src/tty.rs
@@ -211,6 +211,7 @@ pub fn new<T: ToWinsize>(config: &Config, options: &Options, size: &T, window_id
     builder.env("SHELL", shell.program());
     builder.env("HOME", pw.dir);
     builder.env("TERM", "xterm-256color"); // default term until we can supply our own
+    builder.env("COLORTERM", "truecolor"); // advertise 24-bit support
     if let Some(window_id) = window_id {
         builder.env("WINDOWID", format!("{}", window_id));
     }