Diff improvements (#23553)

- Avoid flash of wrong tree toggle icon on page load by setting icon
based on sync state
- Avoid "pop-in" of tree on page load by leaving space based on sync
state
- Use the same border/box-shadow combo used on comment `:target` also
for file `:target`.
- Refactor `DiffFileTree.vue` to use `toggleElem` instead of hardcoded
class name.
- Left-align inline comment boxes and make them fit the same amount of
markup content on a line as GitHub.
- Fix height of `diff-file-list`

Fixes: https://github.com/go-gitea/gitea/issues/23593

<img width="1250" alt="Screenshot 2023-03-18 at 00 52 04"
src="https://user-images.githubusercontent.com/115237/226071392-6789a644-aead-4756-a77e-aba3642150a0.png">
<img width="1246" alt="Screenshot 2023-03-18 at 00 59 43"
src="https://user-images.githubusercontent.com/115237/226071443-8bcba924-458b-48bd-b2f0-0de59cb180ac.png">
<img width="1250" alt="Screenshot 2023-03-18 at 01 27 14"
src="https://user-images.githubusercontent.com/115237/226073121-ccb99f9a-d3ac-40b7-9589-43580c4a01c9.png">
<img width="1231" alt="Screenshot 2023-03-19 at 21 44 16"
src="https://user-images.githubusercontent.com/115237/226207951-81bcae1b-6b41-4e39-83a7-0f37951df6be.png">

(Yes I'm aware the border-radius in bottom corners is suboptimal, but
this would be notorously hard to fix without relying on `overflow:
hidden`).

web_src/css/base.css

@@ -238,6 +238,10 @@ table {
   border-collapse: collapse;
 }
 
+button {
+  cursor: pointer;
+}
+
 details summary {
   cursor: pointer;
 }

web_src/css/repository.css

@@ -1616,14 +1616,12 @@
   padding: 7px 0;
   background: var(--color-body);
   line-height: 30px;
-  height: 47px; /* match .ui.attached.header.diff-file-header.sticky-2nd-row */
 }
 
 @media (max-width: 991px) {
   .repository .diff-detail-box {
     flex-direction: column;
     align-items: flex-start;
-    height: 77px; /* match .ui.attached.header.diff-file-header.sticky-2nd-row */
   }
 }
 
@@ -1679,6 +1677,13 @@
   }
 }
 
+.diff-detail-actions {
+  /* prevent font-size from increasing element height so that .diff-detail-box comes
+     out with height of 47px (one line) and 77px (two lines), which is important for
+     position: sticky */
+  height: 33px;
+}
+
 .repository .diff-detail-box .diff-detail-actions > * {
   margin-right: 0;
 }
@@ -1853,10 +1858,24 @@
   padding-bottom: 5px;
 }
 
+.diff-file-box {
+  border: 1px solid transparent;
+  border-radius: var(--border-radius);
+}
+
+/* TODO: this can potentially be made "global" by removing the class prefix */
+.diff-file-box .ui.attached.header,
+.diff-file-box .ui.attached.table {
+  margin: 0; /* remove fomantic negative margins */;
+  width: initial; /* remove fomantic over 100% width */;
+  max-width: initial; /* remove fomantic over 100% width */;
+}
+
 .repository .diff-stats {
   clear: both;
   margin-bottom: 5px;
-  max-height: 400px;
+  max-height: 200px;
+  height: fit-content;
   overflow: auto;
   padding-left: 0;
 }
@@ -2652,7 +2671,8 @@
   filter: drop-shadow(-3px 0 0 var(--color-primary-alpha-30)) !important;
 }
 
-.code-comment:target {
+.code-comment:target,
+.diff-file-box:target {
   border-color: var(--color-primary) !important;
   border-radius: var(--border-radius) !important;
   box-shadow: 0 0 0 3px var(--color-primary-alpha-30) !important;
@@ -3226,17 +3246,28 @@ td.blob-excerpt {
 }
 
 #diff-file-tree {
-  width: 20%;
+  flex: 0 0 20%;
   max-width: 380px;
   line-height: inherit;
   position: sticky;
   padding-top: 0;
   top: 47px;
-  max-height: calc(100vh - 50px);
+  max-height: calc(100vh - 47px);
   height: 100%;
   overflow-y: auto;
 }
 
+.diff-toggle-file-tree-button {
+  background: none;
+  border: none;
+  user-select: none;
+  color: inherit;
+}
+
+.diff-toggle-file-tree-button:hover {
+  color: var(--color-primary);
+}
+
 @media (max-width: 991px) {
   #diff-file-tree {
     display: none !important;

web_src/css/review.css

@@ -67,8 +67,7 @@
 .comment-code-cloud {
   padding: 0.5rem 1rem !important;
   position: relative;
-  margin: 0 auto;
-  max-width: 1000px;
+  max-width: 820px;
 }
 
 @media (max-width: 767px) {
@@ -308,11 +307,3 @@ a.blob-excerpt:hover {
   width: 72px;
   height: 10px;
 }
-
-.diff-file-box {
-  border-radius: 0.285rem; /* Just like ui.top.attached.header */
-}
-
-.diff-file-box:target {
-  box-shadow: 0 0 0 3px var(--color-accent);
-}