Resolves: #2026895 - Overwrite PROMPT only if it's set to the built-in default

Fedora bug: https://bugzilla.redhat.com/show_bug.cgi?id=2026749

zsh.spec

@@ -1,7 +1,7 @@
 Summary: Powerful interactive shell
 Name: zsh
 Version: 5.8
-Release: 7%{?dist}
+Release: 8%{?dist}
 License: MIT
 URL: http://zsh.sourceforge.net/
 Source0: https://downloads.sourceforge.net/%{name}/%{name}-%{version}.tar.xz
@@ -158,6 +158,9 @@ fi
 %doc Doc/*.html
 
 %changelog
+* Thu Nov 25 2021 Debarshi Ray <rishi@fedoraproject.org> - 5.8-8
+- Overwrite PROMPT only if it's set to the built-in default (#2026749)
+
 * Tue Aug 10 2021 Mohan Boddu <mboddu@redhat.com> - 5.8-7
 - Rebuilt for IMA sigs, glibc 2.34, aarch64 flags
   Related: rhbz#1991688

zshrc.rhs

@@ -8,7 +8,7 @@
 #setenv() { export $1=$2 }  # csh compatibility
 
 # Set prompts
-PROMPT='[%n@%m]%~%# '    # default prompt
+[[ "$PROMPT" = "%m%# " ]] && PROMPT='[%n@%m]%~%# '    # default prompt
 #RPROMPT=' %~'     # prompt for right side of screen
 
 # bindkey -v             # vi key bindings