Avoid extra slashes in redirects with :splat

Remove leading slashes from captured portions of paths when
redirecting using splats. This makes a directive like
"/articles/*  /posts/:splat  302" behave as described in
FEATURES.md, i.e. "/articles/foo" now redirects to
"/posts/foo" rather than to "/posts//foo". Fixes #269.

This also changes the behavior of a redirect like
"/articles/*  /posts:splat  302". "/articles/foo" will now
redirect to "/postsfoo" rather than to "/posts/foo".

This change also fixes an issue where paths like
"/articles123" would be incorrectly matched by the above
patterns.

server/handler/try.go

@@ -1,7 +1,6 @@
 package handler
 
 import (
-	"fmt"
 	"net/http"
 	"strings"
 
@@ -42,7 +41,7 @@ func tryUpstream(ctx *context.Context, giteaClient *gitea.Client,
 
 	// Try to request the file from the Gitea API
 	if !options.Upstream(ctx, giteaClient, redirectsCache) {
-		html.ReturnErrorPage(ctx, fmt.Sprintf("Forge returned %d %s", ctx.StatusCode, http.StatusText(ctx.StatusCode)), ctx.StatusCode)
+		html.ReturnErrorPage(ctx, "forge client failed", ctx.StatusCode)
 	}
 }