plugins/airline: switch to mkPlugin + refactoring

tests/test-sources/plugins/statuslines/airline.nix

@@ -0,0 +1,82 @@
+{
+  empty = {
+    plugins.airline.enable = true;
+  };
+
+  example = {
+    plugins.airline = {
+      enable = true;
+
+      sectionA = "foo";
+      sectionB = "foo";
+      sectionC = "foo";
+      sectionX = "foo";
+      sectionY = "foo";
+      sectionZ = "foo";
+      experimental = true;
+      leftSep = ">";
+      rightSep = "<";
+      detectModified = true;
+      detectPaste = true;
+      detectCrypt = true;
+      detectSpell = true;
+      detectSpelllang = true;
+      detectIminsert = false;
+      inactiveCollapse = true;
+      inactiveAltSep = true;
+      theme = "dark";
+      themePatchFunc = null;
+      powerlineFonts = false;
+      symbolsAscii = false;
+      modeMap = {
+        __ = "-";
+        c = "C";
+        i = "I";
+        ic = "I";
+        ix = "I";
+        n = "N";
+        multi = "M";
+        ni = "N";
+        no = "N";
+        R = "R";
+        Rv = "R";
+        s = "S";
+        S = "S";
+        t = "T";
+        v = "V";
+        V = "V";
+      };
+      excludeFilenames = [];
+      excludeFiletypes = [];
+      filetypeOverrides = {
+        coc-explorer = ["CoC Explorer" ""];
+        defx = ["defx" "%{b:defx.paths[0]}"];
+        fugitive = ["fugitive" "%{airline#util#wrap(airline#extensions#branch#get_head(),80)}"];
+        gundo = ["Gundo" ""];
+        help = ["Help" "%f"];
+        minibufexpl = ["MiniBufExplorer" ""];
+        startify = ["startify" ""];
+        vim-plug = ["Plugins" ""];
+        vimfiler = ["vimfiler" "%{vimfiler#get_status_string()}"];
+        vimshell = ["vimshell" "%{vimshell#get_status_string()}"];
+        vaffle = ["Vaffle" "%{b:vaffle.dir}"];
+      };
+      excludePreview = false;
+      disableStatusline = false;
+      skipEmptySections = true;
+      highlightingCache = false;
+      focuslostInactive = false;
+      statuslineOntop = false;
+      stlPathStyle = "short";
+      sectionCOnlyFilename = true;
+      symbols = {
+        branch = "";
+        colnr = " ℅:";
+        readonly = "";
+        linenr = " :";
+        maxlinenr = "☰ ";
+        dirty = "⚡";
+      };
+    };
+  };
+}