refactor(git): drive :G dispatch from buffer content

lua/git/cmd.lua

@@ -7,90 +7,13 @@ local M = {}
 
 ---@class ow.Git.Cmd.SplitHandler
 ---@field ft string
----@field needs_rev boolean?
----@field on_state? fun(state: ow.Git.Repo.BufState, r: ow.Git.Repo, args: string[])
-
----@param r ow.Git.Repo
----@param args string[]  -- diff args including leading "diff"
----@return string left_ref
----@return string? right_ref  -- nil means worktree
-local function compute_diff_refs(r, args)
-    local cached = false
-    local positional = {} ---@type string[]
-    local saw_separator = false
-    for i = 2, #args do
-        local a = args[i]
-        if saw_separator then
-            break
-        elseif a == "--" then
-            saw_separator = true
-        elseif a == "--cached" or a == "--staged" then
-            cached = true
-        elseif a:sub(1, 1) ~= "-" then
-            table.insert(positional, a)
-        end
-    end
-
-    local function defaults()
-        if cached then
-            return "HEAD", ":"
-        end
-        return ":", nil
-    end
-
-    if #positional == 0 then
-        return defaults()
-    end
-
-    local first = positional[1] --[[@as string]]
-    if #positional == 1 then
-        local lhs, rhs = first:match("^(.-)%.%.%.(.+)$")
-        if lhs then
-            return (lhs ~= "" and lhs or "HEAD"), rhs
-        end
-        lhs, rhs = first:match("^(.-)%.%.(.+)$")
-        if lhs then
-            return (lhs ~= "" and lhs or "HEAD"),
-                (rhs ~= "" and rhs or "HEAD")
-        end
-        if r:rev_parse(first, true) then
-            if cached then
-                return first, ":"
-            end
-            return first, nil
-        end
-        return defaults()
-    end
-
-    local second = positional[2] --[[@as string]]
-    local first_ok = r:rev_parse(first, true) ~= nil
-    if first_ok and r:rev_parse(second, true) then
-        return first, second
-    end
-    if first_ok then
-        if cached then
-            return first, ":"
-        end
-        return first, nil
-    end
-    return defaults()
-end
 
 ---@type table<string, ow.Git.Cmd.SplitHandler>
 local SPLIT_HANDLERS = {
     log = { ft = "git" },
-    diff = {
-        ft = "gitdiff",
-        on_state = function(state, r, args)
-            local left, right = compute_diff_refs(r, args)
-            state.left_ref = left
-            state.right_ref = right
-        end,
-    },
+    diff = { ft = "git" },
 }
 
-M._compute_diff_refs = compute_diff_refs
-
 ---@type string[]?
 local cached_cmds
 
@@ -207,28 +130,16 @@ function M.parse_args(line)
     return args
 end
 
----@param args string[]
----@param start integer
----@return string?
-local function first_positional(args, start)
-    for i = start, #args do
-        local a = args[i]
-        if a:sub(1, 1) ~= "-" then
-            return a
-        end
-    end
-end
-
 ---@param name string
 ---@return integer buf
 local function place_split(name)
-    local buf = vim.fn.bufnr("\\V" .. name)
-    if buf == -1 then
-        buf = util.new_scratch({ name = name, bufhidden = "hide" })
-        return buf
-    end
+    -- bufadd resolves the name the same way nvim_buf_set_name does
+    -- (cwd-prefixing for non-absolute names), so calling it twice with
+    -- the same name returns the same buffer.
+    local buf = vim.fn.bufadd(name)
     if not vim.api.nvim_buf_is_loaded(buf) then
         vim.fn.bufload(buf)
+        util.setup_scratch(buf, { bufhidden = "hide" })
     end
     local win = vim.fn.bufwinid(buf)
     if win ~= -1 then
@@ -278,9 +189,7 @@ end
 ---@param args string[]
 ---@param conf ow.Git.Cmd.SplitHandler
 local function run_in_split(r, args, conf)
-    local cmd = { "git" }
-    vim.list_extend(cmd, args)
-    util.exec(cmd, {
+    util.git(args, {
         cwd = r.worktree,
         on_done = function(stdout)
             if not stdout then
@@ -291,19 +200,6 @@ local function run_in_split(r, args, conf)
             object.attach_dispatch(buf)
             attach_history_keys(buf)
             local state = r:state(buf) --[[@as -nil]]
-            state.sha = nil
-            state.parent_sha = nil
-            if conf.needs_rev then
-                local user_rev = first_positional(args, 2) or "HEAD"
-                local sha = r:rev_parse(user_rev, true)
-                if sha then
-                    state.sha = sha
-                    state.parent_sha = r:rev_parse(user_rev .. "^", true)
-                end
-            end
-            if conf.on_state then
-                conf.on_state(state, r, args)
-            end
             vim.bo[buf].filetype = conf.ft
             -- Force a new undo block so each rerun is its own undo step.
             vim.bo[buf].undolevels = vim.bo[buf].undolevels
@@ -386,7 +282,7 @@ function M.run(args)
             object.open(r, args[2])
             return
         end
-        run_in_split(r, args, { ft = "git", needs_rev = true })
+        run_in_split(r, args, { ft = "git" })
         return
     end
 
@@ -395,7 +291,7 @@ function M.run(args)
             object.open(r, args[3])
             return
         end
-        run_in_split(r, args, { ft = "git", needs_rev = true })
+        run_in_split(r, args, { ft = "git" })
         return
     end