refactor(git): make the git module self-contained under git.util

lua/git/show.lua

@@ -1,8 +1,7 @@
 local diff = require("git.diff")
 local git = require("git")
-local log = require("log")
 local repo = require("git.repo")
-local util = require("util")
+local util = require("git.util")
 
 local M = {}
 
@@ -109,7 +108,7 @@ end
 ---@param section ow.Git.DiffSection
 local function show_diff(ctx, section)
     if not section.pre_blob or not section.post_blob then
-        log.warning("no index line; cannot determine blob SHAs")
+        util.warning("no index line; cannot determine blob SHAs")
         return
     end
     local parent = ctx.parent_ref or "0"
@@ -152,7 +151,7 @@ function M.open_commit(worktree, ref, opts)
         return
     end
 
-    local stdout = util.system_sync({ "git", "show", ref }, { cwd = worktree })
+    local stdout = util.exec({ "git", "show", ref }, { cwd = worktree })
     if not stdout then
         return
     end