Enable revive linter, and fix a bunch of warnings

I took the set of enabled checks from revive's recommended configuration [1],
and removed some that I didn't like. There might be other useful checks in
revive that we might want to enable, but this is a nice improvement already.

The bulk of the changes here are removing unnecessary else statements after
returns, but there are a few others too.

[1] https://github.com/mgechev/revive?tab=readme-ov-file#recommended-configuration

pkg/gui/presentation/commits.go

@@ -145,9 +145,8 @@ func GetCommitListDisplayStrings(
 			getGraphLine = func(idx int) string {
 				if idx >= graphOffset {
 					return graphLines[idx-graphOffset]
-				} else {
-					return ""
 				}
+				return ""
 			}
 		}
 	} else {
@@ -305,9 +304,8 @@ func getBisectStatus(index int, commitHash string, bisectInfo *git_commands.Bise
 	} else {
 		if bisectBounds != nil && index >= bisectBounds.newIndex && index <= bisectBounds.oldIndex {
 			return BisectStatusCandidate
-		} else {
-			return BisectStatusNone
 		}
+		return BisectStatusNone
 	}
 
 	// should never land here