feat: add support for fossil-scm in prompt (#9500)

* feat: add support for fossil-scm in prompt

* fix: change directory testing and string matching

(cherry picked from commit cf67709931)

share/functions/fish_fossil_prompt.fish

@@ -0,0 +1,53 @@
+function fish_fossil_prompt --description 'Write out the fossil prompt'
+    # Bail if fossil is not available
+    if not command -sq fossil
+        return 1
+    end
+
+    # Bail if not a fossil checkout
+    if not fossil ls &> /dev/null
+	return 127
+    end
+
+    # Parse fossil info
+    set -l fossil_info (fossil info)
+    string match --regex --quiet \
+        '^project-name:\s*(?<fossil_project_name>.*)$' $fossil_info
+    string match --regex --quiet \
+        '^tags:\s*(?<fossil_tags>.*)$' $fossil_info
+
+    echo -n ' ['
+    set_color --bold magenta
+    echo -n $fossil_project_name
+    set_color normal
+    echo -n ':'
+    set_color --bold yellow
+    echo -n $fossil_tags
+    set_color normal
+
+    # Parse fossil status
+    set -l fossil_status (fossil status)
+    if string match --quiet 'ADDED*' $fossil_status
+        set_color --bold green
+        echo -n '+'
+    end
+    if string match --quiet 'DELETED*' $fossil_status
+        set_color --bold red
+        echo -n '-'
+    end
+    if string match --quiet 'MISSING*' $fossil_status
+        set_color --bold red
+        echo -n '!'
+    end
+    if string match --quiet 'RENAMED*' $fossil_status
+        set_color --bold yellow
+        echo -n '→'
+    end
+    if string match --quiet 'CONFLICT*' $fossil_status
+        set_color --bold green
+        echo -n '×'
+    end
+
+    set_color normal
+    echo -n ']'
+end

share/functions/fish_vcs_prompt.fish

@@ -3,6 +3,7 @@ function fish_vcs_prompt --description "Print all vcs prompts"
     # This is so we don't try svn if git already worked.
     fish_git_prompt $argv
     or fish_hg_prompt $argv
+    or fish_fossil_prompt $argv
     # The svn prompt is disabled by default because it's quite slow on common svn repositories.
     # To enable it uncomment it.
     # You can also only use it in specific directories by checking $PWD.