cgit-about-filter: keep the branch in links

1 files changed, 32 insertions, 2 deletions

diff --git a/pkgs/simple/cgit-about-filter/cgit-about-filter.lua b/pkgs/simple/cgit-about-filter/cgit-about-filter.lua
index 64e16fa..6e1ccdd 100644
--- a/pkgs/simple/cgit-about-filter/cgit-about-filter.lua
+++ b/pkgs/simple/cgit-about-filter/cgit-about-filter.lua
@@ -22,6 +22,30 @@ local function resolve(base, relative)
     return prefix .. table.concat(segments, "/")
 end
 
+-- The branch from the query string (?h=...), or nil.  cgit doesn't pass it
+-- to filters, but Lua filters run in cgit's process, which has the CGI
+-- environment.
+local function query_head()
+    local query = os.getenv("QUERY_STRING") or ""
+    for key, value in query:gmatch("([^&=]+)=([^&]*)") do
+        if key == "h" then
+            value = value:gsub("%+", " "):gsub("%%(%x%x)", function(hex)
+                return string.char(tonumber(hex, 16))
+            end)
+            if value ~= "" then
+                return value
+            end
+        end
+    end
+    return nil
+end
+
+local function url_escape(s)
+    return (s:gsub("[^%w._~/-]", function(c)
+        return string.format("%%%02X", c:byte())
+    end))
+end
+
 local buffer = ""
 local should_render = true
 local current_dir = "" -- Stores the directory prefix of the file being processed
@@ -67,6 +91,12 @@ function filter_close()
 
     local repo = os.getenv("CGIT_REPO_URL") or ""
 
+    local head = query_head()
+    local query = ""
+    if head and head ~= os.getenv("CGIT_REPO_DEFBRANCH") then
+        query = "?h=" .. url_escape(head)
+    end
+
     local processed = buffer:gsub("%[([^%]]+)%]%(([^:)]+)%)", function(text, path)
         -- Ignore protocols (http, https, etc.), absolute paths (/), and anchors (#)
         if path:sub(1, 1) == "/" or path:sub(1, 1) == "#" or path:match("^%w+:") then
@@ -79,9 +109,9 @@ function filter_close()
         path = resolve(current_dir, path)
 
         if path:sub(-3) == ".md" then
-          return string.format("[%s](/%s/about/%s%s)", text, repo, path, fragment)
+          return string.format("[%s](/%s/about/%s%s%s)", text, repo, path, query, fragment)
         else
-          return string.format("[%s](/%s/tree/%s%s)", text, repo, path, fragment)
+          return string.format("[%s](/%s/tree/%s%s%s)", text, repo, path, query, fragment)
         end
     end)