Add whitespace handling to PR-comparsion (#4683)

* Add whitespace handling to PR-comparsion

In a PR we have to keep an eye on a lot of different things. But sometimes the
bare code is the key-thing we want to care about and just don't want to care
about fixed indention on some places. Especially if we follow the pathfinder
rule we face a lot of these situations because these changes don't break the
code in many languages but improve the readability a lot.

So this change introduce a fine graned button to adjust the way how the
reviewer want to see whitespace-changes within the code.

The possibilities reflect the possibilities from git itself except of the
`--ignore-blank-lines` flag because that one is also handled by `-b` and is
really rare.

Signed-off-by: Felix Nehrke <felix@nehrke.info>

routers/repo/middlewares.go

@@ -50,3 +50,14 @@ func SetDiffViewStyle(ctx *context.Context) {
 		ctx.ServerError("ErrUpdateDiffViewStyle", err)
 	}
 }
+
+// SetWhitespaceBehavior set whitespace behavior as render variable
+func SetWhitespaceBehavior(ctx *context.Context) {
+	whitespaceBehavior := ctx.Query("whitespace")
+	switch whitespaceBehavior {
+	case "ignore-all", "ignore-eol", "ignore-change":
+		ctx.Data["WhitespaceBehavior"] = whitespaceBehavior
+	default:
+		ctx.Data["WhitespaceBehavior"] = ""
+	}
+}