[Bug] performance: consider GIT_OPTIONAL_LOCKS

[emmanueltouzery]

Description

I'm using diffview to review my commits. My workflow is to stage individual files in diffview. Staging each file will causes diffview to update its display, which is the right way. However I feel that after doing that for a while, the performance degrades. Staging a single file can take in the range of one second.

I have multiple neovim plugins which make git calls, too. For instance nvim-tree, which at these times throws me warnings saying that it's disabling its git integration because 5 git calls took more than 400ms.

Because the initial performance is good, I now think that the issue is caused by git lock contention. I see that most other neovim plugins using git make use of the --no-optional-locks flag to reduce contention, but diffview doesn't.

My theory is that adding --no-optional-locks in places where it would make sense within diffview should help with the performance issues I've been seeing.

Expected behavior

No response

Actual behavior

Getting poor performance after long diffview use and staging/diffing many files.

Steps to reproduce

I can't really reproduce this on-demand. However one thing I'm trying recently is to force diffview to use no-optional-locks on all its calls. The way I achieved that is by patching my lua/diffview/job.lua:

local function prepare_env(env)
-  local ret = {}
+  local ret = {"GIT_OPTIONAL_LOCKS=0"}

  for k, v in pairs(env) do
    table.insert(ret, k .. "=" .. v)
  end

I've been running diffview with this change for a while and noticed no issues, and I didn't get serious slowdowns since then (but then again I wasn't getting them that often, so it's not definitive proof that it helps yet).

Health check

Output of :checkhealth diffview

==============================================================================
diffview: require("diffview.health").check()

Checking plugin dependencies ~
- OK nvim-web-devicons installed.

Checking VCS tools ~
- The plugin requires at least one of the supported VCS tools to be valid.
- OK Git found.
- OK Git is up-to-date. (2.47.0)
- OK Mercurial found.
- OK Mercurial is up-to-date. (6.7.4)

Log info

Relevant info from :DiffviewLog

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Neovim version

NVIM v0.10.1
Build type: Release
LuaJIT 2.1.1713484068

Operating system and version

Linux 6.10.12-200.fc40.x86_64 x86_64 GNU/Linux

Minimal config

No response