Handle repos with a large number of filesHEADmaster

It would previously blow the stack when trying to run spawn, since it
unpacks the args at one point.

1 files changed, 24 insertions, 8 deletions

diff --git a/tar-clone.lua b/tar-clone.lua
index 582fd94..358a1b6 100755
--- a/tar-clone.lua
+++ b/tar-clone.lua
@@ -229,24 +229,38 @@ local function list_tree(repo, HEAD)
 	return output:gmatch"([^ ]+) ([^ ]+) ([^ ]+)\t([^%z]+)%z"
 end
 
-local function write_index(writer, repo, HEAD, localname)
+local function update_index(repo, HEAD, index)
+	local function exec(args)
+		args.cwd = repo
+		args.env = {GIT_INDEX_FILE = index}
+		local proc = sp.spawn_simple(args)
+		local how, why = proc:wait()
+		if how == -1 then
+			error("git update-index failed: "..tostring(why))
+		end
+	end
 	local cmdline = {"git", "update-index", "--add"}
 	for mode, kind, sha1, path in list_tree(repo, HEAD) do
 		table.insert(cmdline, "--cacheinfo")
 		table.insert(cmdline, mode)
 		table.insert(cmdline, sha1)
 		table.insert(cmdline, path)
+		if #cmdline >= 50 then -- arbitrary limit
+			exec(cmdline)
+			cmdline = {"git", "update-index", "--add"}
+		end
 	end
+	if #cmdline > 3 then
+		exec(cmdline)
+	end
+end
+
+local function write_index(writer, repo, HEAD, localname)
 	local dir = mkdtemp()
 	local index = dir..'/index'
 
-	cmdline.cwd = repo
-	cmdline.env = {GIT_INDEX_FILE = index}
-	local proc = sp.spawn_simple(cmdline)
-	local how, why = proc:wait()
-	if how == -1 then
-		error("git update-index failed: "..tostring(why))
-	end
+	update_index(repo, HEAD, index)
+
 	local entry = archive.entry{
 		sourcepath = index,
 		pathname = localname..'/.git/index',
@@ -293,3 +307,5 @@ write_refs(writer, repo, HEAD, localname)
 write_workspace(writer, repo, HEAD, localname)
 
 write_index(writer, repo, HEAD, localname)
+
+writer:close()