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

lua/git/repo.lua

@@ -15,9 +15,6 @@ end
 ---@class ow.Git.Repo.BufState
 ---@field repo ow.Git.Repo
 ---@field sha string?
----@field parent_sha string?
----@field left_ref string?
----@field right_ref string?
 ---@field initialized boolean?
 ---@field immutable boolean?
 ---@field index_writer boolean?
@@ -318,6 +315,30 @@ function Repo:rev_parse(rev, short)
     return trimmed ~= "" and trimmed or nil
 end
 
+---@alias ow.Git.Repo.ResolveStatus "ok"|"ambiguous"|"missing"
+
+---@param prefix string
+---@return string? full_sha
+---@return ow.Git.Repo.ResolveStatus
+function Repo:resolve_sha(prefix)
+    local result = self:get_cached("resolve:" .. prefix, function(self)
+        local out = util.exec(
+            { "git", "rev-parse", "--disambiguate=" .. prefix },
+            { cwd = self.worktree, silent = true }
+        )
+        local trimmed = out and vim.trim(out) or ""
+        if trimmed == "" then
+            return { nil, "missing" }
+        end
+        local lines = util.split_lines(trimmed)
+        if #lines == 1 then
+            return { lines[1], "ok" }
+        end
+        return { nil, "ambiguous" }
+    end)
+    return result[1], result[2]
+end
+
 ---@type table<string, ow.Git.Repo> keyed by worktree
 local repos = {}