irmin-git: fix decoding contents in the middle of a buffer

CHANGES.md

@@ -26,6 +26,11 @@
     the maintenance of that part of the code, as ensuring the correct order of
     cached IO operations was tricky for stream proofs (#2275, @samoht)
 
+### Changed
+
+- **irmin-git**
+  - Moved lower bounds to `git.3.14.0` to use new function (#2277, @metanivek)
+
 ## 3.8.0 (2023-07-06)
 
 ### Added

examples/server/config.ml

@@ -14,6 +14,11 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  *)
 
-module Store = Irmin_mem.KV.Make (Irmin.Contents.String)
+module Store = struct
+  module Git_impl = Irmin_git.Mem
+  module Sync = Git.Mem.Sync (Git_impl)
+  module Maker = Irmin_git.KV (Git_impl) (Sync)
+  include Maker.Make (Irmin.Contents.String)
+end
 
 let uri = Uri.of_string "tcp://localhost:4242"

irmin-git.opam

@@ -19,8 +19,8 @@ depends: [
   "dune"       {>= "2.9.0"}
   "irmin"      {= version}
   "ppx_irmin"  {= version}
-  "git"        {>= "3.7.0"}
-  "git-unix"   {>= "3.7.0"}
+  "git"        {>= "3.14.0"}
+  "git-unix"   {>= "3.14.0"}
   "digestif"   {>= "0.9.0"}
   "cstruct"
   "fmt"

src/irmin-git/contents.ml

@@ -52,9 +52,10 @@ module Make (G : Git.S) (C : Irmin.Contents.S) = struct
       match Raw.of_raw_with_header ~off buf with
       | Ok g -> (
           match V.of_git g with
-          | Some g ->
-              pos_ref := String.length buf;
-              g
+          | Some v ->
+              let len = Raw.length_with_header g |> Int64.to_int in
+              pos_ref := off + len;
+              v
           | None -> failwith "wrong object kind")
       | Error (`Msg _) -> failwith "wrong object"