ui-diff: Add links to increase/decrease number of context lines in diffs

Add two links to the "Diffstat" line to show more/less context lines in the
generated diff.

To support this, cgit_commit_link() and cgit_diff_link() has learned to
preserve the ctx.qry.context variable.

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

ui-diff.c

@@ -156,13 +156,21 @@ static void inspect_filepair(struct diff_filepair *pair)
 void cgit_print_diffstat(const unsigned char *old_sha1,
 			 const unsigned char *new_sha1, const char *prefix)
 {
-	int i;
+	int i, save_context = ctx.qry.context;
 
 	html("<div class='diffstat-header'>");
 	cgit_diff_link("Diffstat", NULL, NULL, ctx.qry.head, ctx.qry.sha1,
 		       ctx.qry.sha2, NULL, 0);
 	if (prefix)
 		htmlf(" (limited to '%s')", prefix);
+	html(" (");
+	ctx.qry.context = (save_context > 0 ? save_context : 3) << 1;
+	cgit_self_link("more", NULL, NULL, &ctx);
+	html("/");
+	ctx.qry.context = (save_context > 3 ? save_context : 3) >> 1;
+	cgit_self_link("less", NULL, NULL, &ctx);
+	ctx.qry.context = save_context;
+	html(" context)");
 	html("</div>");
 	html("<table summary='diffstat' class='diffstat'>");
 	max_changes = 0;

ui-shared.c

@@ -341,6 +341,13 @@ void cgit_commit_link(char *name, const char *title, const char *class,
 	if ((ctx.qry.ssdiff && !toggle_ssdiff) || (!ctx.qry.ssdiff && toggle_ssdiff)) {
 		html(delim);
 		html("ss=1");
+		delim = "&";
+	}
+	if (ctx.qry.context > 0 && ctx.qry.context != 3) {
+		html(delim);
+		html("context=");
+		htmlf("%d", ctx.qry.context);
+		delim = "&";
 	}
 	html("'>");
 	html_txt(name);
@@ -382,6 +389,13 @@ void cgit_diff_link(const char *name, const char *title, const char *class,
 	if ((ctx.qry.ssdiff && !toggle_ssdiff) || (!ctx.qry.ssdiff && toggle_ssdiff)) {
 		html(delim);
 		html("ss=1");
+		delim = "&";
+	}
+	if (ctx.qry.context > 0 && ctx.qry.context != 3) {
+		html(delim);
+		html("context=");
+		htmlf("%d", ctx.qry.context);
+		delim = "&";
 	}
 	html("'>");
 	html_txt(name);