Replace `1;38` with `1;37` (bold white) in the delimiter/header
color constant. SGR parameter 38 is the extended foreground color
prefix and requires sub-parameters (e.g. `38;5;n` or `38;2;r;g;b`),
so using it bare produces an invalid escape sequence. Most terminals
silently ignore the malformed parameter, masking the bug.
Fixescli/cli#12683
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
In the absence of an explicit `--color` setting, or when `--color=auto`
is passed, the pr diff command should fall back to respecting the global
colorization setting as inferred from the environment.
If the `--repo` flag is specified, then the user intends to select a
repository other than the current one. In that case, it doesn't make
sense to fall back to detecting the PR belonging to the current branch,
so throw a descriptive error instead.
