fix(git): reuse existing buffer instead of swallowing E95

lua/git/show.lua

@@ -88,15 +88,20 @@ end
 ---@param ref string  the commit ref the blob represents (e.g. `<sha>` or `<sha>^`)
 ---@return integer
 local function blob_buf(worktree, blob, path, ref)
+    local name = "git://" .. ref .. "/" .. path
+    -- Reuse an existing buffer with this name (commit refs and blobs are
+    -- immutable, so the content is stable); avoids E95 collisions and
+    -- prevents accumulating duplicate buffers as the user navigates.
+    local existing = vim.fn.bufnr(name)
+    if existing ~= -1 and vim.api.nvim_buf_is_loaded(existing) then
+        return existing
+    end
     if is_zero(blob) then
-        return diff.empty_buf({
-            name = "git://" .. ref .. "/" .. path,
-            bufhidden = "hide",
-        })
+        return diff.empty_buf({ name = name, bufhidden = "hide" })
     end
     ---@cast blob string
     local buf = diff.git_show_blob(worktree, blob)
-    diff.set_buf_name_and_filetype(buf, "git://" .. ref .. "/" .. path)
+    diff.set_buf_name_and_filetype(buf, name)
     return buf
 end
 
@@ -133,6 +138,17 @@ end
 ---@param worktree string
 ---@param ref string
 function M.open_commit(worktree, ref)
+    local sha = repo.rev_parse(worktree, ref, true) or ref
+    local name = "git://" .. sha .. "/"
+    -- Reuse a previously-opened buffer for the same commit; commit SHAs
+    -- are immutable so the content is stable.
+    local existing = vim.fn.bufnr(name)
+    if existing ~= -1 and vim.api.nvim_buf_is_loaded(existing) then
+        vim.cmd("normal! m'")
+        vim.cmd("buffer " .. existing)
+        return
+    end
+
     local result = vim.system(
         { "git", "show", ref },
         { cwd = worktree, text = true }
@@ -143,7 +159,6 @@ function M.open_commit(worktree, ref)
         return
     end
     local lines = util.split_lines(result.stdout or "")
-    local sha = repo.rev_parse(worktree, ref, true) or ref
     local parent = repo.rev_parse(worktree, ref .. "^", true)
     local buf = vim.api.nvim_create_buf(false, true)
     vim.bo[buf].buftype = "nofile"
@@ -152,7 +167,7 @@ function M.open_commit(worktree, ref)
     vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
     vim.bo[buf].modifiable = false
     vim.bo[buf].modified = false
-    pcall(vim.api.nvim_buf_set_name, buf, "git://" .. sha .. "/")
+    pcall(vim.api.nvim_buf_set_name, buf, name)
     vim.b[buf].git_worktree = worktree
     vim.b[buf].git_ref = sha
     vim.b[buf].git_parent_ref = parent