Branch page and misc css improvements (#15208) (#15274)

- Improve branches page, increase icon size, use octicons, use css vars
- Style placeholder color via css var
- Slightly increase contrast of input fields and active/hover states
- Add styling for select boxes in arc-green

web_src/less/_base.less

@@ -98,8 +98,8 @@
   --color-navbar: #f8f8f8;
   --color-light: #00000004;
   --color-light-border: #0000001d;
-  --color-hover: #0000000d;
-  --color-active: #00000012;
+  --color-hover: #0000000f;
+  --color-active: #00000014;
   --color-menu: #ffffff;
   --color-card: #ffffff;
   --color-markdown-table-row: #00000008;
@@ -109,6 +109,7 @@
   --color-markdown-code-block: #00000010;
   --color-secondary-bg: #f4f4f4;
   --color-expand-button: #d8efff;
+  --color-placeholder-text: #aaa;
   /* backgrounds */
   --checkbox-mask-checked: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="-1 -1 18 18" width="16" height="16"><path fill-rule="evenodd" d="M13.78 4.22a.75.75 0 010 1.06l-7.25 7.25a.75.75 0 01-1.06 0L2.22 9.28a.75.75 0 011.06-1.06L6 10.94l6.72-6.72a.75.75 0 011.06 0z"></path></svg>');
   --checkbox-mask-indeterminate: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" width="16" height="16"><path fill-rule="evenodd" d="M2 7.75A.75.75 0 012.75 7h10a.75.75 0 010 1.5h-10A.75.75 0 012 7.75z"></path></svg>');
@@ -188,12 +189,14 @@ table {
 ::selection,
 .CodeMirror-selected {
   background: var(--color-primary-light-1) !important;
-  color: #fff !important;
+  color: var(--color-white) !important;
 }
 
 ::placeholder,
-.CodeMirror-placeholder {
-  color: #aaa !important;
+.CodeMirror-placeholder,
+.ui.dropdown:not(.button) > .default.text,
+.ui.default.dropdown:not(.button) > .text {
+  color: var(--color-placeholder-text) !important;
   opacity: 1 !important;
 }
 
@@ -1972,7 +1975,7 @@ table th[data-sortt-desc] {
 .ui.secondary.pointing.menu .dropdown.item:hover,
 .ui.secondary.pointing.menu .link.item:hover,
 .ui.secondary.pointing.menu a.item:hover {
-  color: var(--color-text);
+  color: var(--color-text-dark);
 }
 
 .ui.header {

web_src/less/_explore.less

@@ -48,7 +48,7 @@
 .ui.repository.branches {
   .info {
     font-size: 12px;
-    color: #808080;
+    color: var(--color-text-light);
     display: flex;
     white-space: pre;
     .commit-message {

web_src/less/_form.less

@@ -2,6 +2,7 @@ input,
 textarea,
 .ui.input > input,
 .ui.form input:not([type]),
+.ui.form select,
 .ui.form textarea,
 .ui.form input[type="date"],
 .ui.form input[type="datetime-local"],
@@ -27,6 +28,7 @@ input:hover,
 textarea:hover,
 .ui.input input:hover,
 .ui.form input:not([type]):hover,
+.ui.form select:hover,
 .ui.form textarea:hover,
 .ui.form input[type="date"]:hover,
 .ui.form input[type="datetime-local"]:hover,
@@ -54,6 +56,7 @@ input:focus,
 textarea:focus,
 .ui.input input:focus,
 .ui.form input:not([type]):focus,
+.ui.form select:focus,
 .ui.form textarea:focus,
 .ui.form input[type="date"]:focus,
 .ui.form input[type="datetime-local"]:focus,
@@ -124,6 +127,11 @@ textarea:focus,
   background: var(--color-primary) !important;
 }
 
+/* match <select> padding to <input> */
+.ui.form select {
+  padding: .67857143em 1em;
+}
+
 .form {
   .help {
     color: #999999;

web_src/less/_repository.less

@@ -1261,7 +1261,7 @@
         max-width: 90px;
 
         &:last-child {
-          border-left: 1px solid var(--color-secondary);
+          border-left: 1px solid var(--color-secondary-dark-2);
         }
       }
 
@@ -1280,7 +1280,7 @@
       .bar {
         height: 4px;
         position: absolute;
-        background-color: var(--color-secondary);
+        background-color: var(--color-secondary-dark-2);
 
         &.bar-behind {
           right: 0;

web_src/less/themes/theme-arc-green.less

@@ -87,14 +87,14 @@
   --color-footer: #2e323e;
   --color-timeline: #4c525e;
   --color-input-text: #d5dbe6;
-  --color-input-background: #2e323e;
+  --color-input-background: #292d39;
   --color-input-border: #454a57;
   --color-input-border-hover: #505667;
   --color-navbar: #2a2e3a;
   --color-light: #00000028;
   --color-light-border: #ffffff28;
-  --color-hover: #60606020;
-  --color-active: #60606040;
+  --color-hover: #ffffff10;
+  --color-active: #ffffff16;
   --color-menu: #2e323e;
   --color-card: #2e323e;
   --color-markdown-table-row: #ffffff06;
@@ -105,10 +105,7 @@
   --color-secondary-bg: #2a2e3a;
   --color-text-focus: #fff;
   --color-expand-button: #3c404d;
-}
-
-.repository.branches .commit-divergence .bar {
-  background: #6a737d;
+  --color-placeholder-text: #6a737d;
 }
 
 .ui.horizontal.segments > .segment {
@@ -119,11 +116,6 @@
   background: var(--color-primary-alpha-20) !important;
 }
 
-::placeholder,
-.CodeMirror-placeholder {
-  color: #6a737d !important;
-}
-
 [data-tooltip]::before,
 [data-tooltip]::after {
   background: #1b1c1d !important; /* .ui.inverted.popup */