feat(diff): Add the diff_history command (#97)

This new command is natively implemented by both the `codediff` and `diffview` backends allowing to easily navigate the changes between two revsets while diffing the. 

It also gives a new `:J diff_hisotyr` command that optionally takes a range of revsets formatted `<rev1>..<rev2>` otherwise it prompts the user for the range.

lua/jj/diff/codediff.lua

@@ -28,6 +28,21 @@ local function diff_two_changes(left, right)
 	vim.cmd(string.format("CodeDiff %s %s", commit_id_right, commit_id_left))
 end
 
+local function diff_two_changes_with_history(left, right)
+	local commit_id_left = utils.get_commit_id(left)
+	if commit_id_left == nil then
+		return
+	end
+
+	local commit_id_right = utils.get_commit_id(right)
+	if commit_id_right == nil then
+		return
+	end
+
+	-- test
+	vim.cmd(string.format("CodeDiff history %s..%s", commit_id_right, commit_id_left))
+end
+
 -----------------------------------------------------------------------
 -- Codediff Backend
 -----------------------------------------------------------------------
@@ -67,4 +82,12 @@ diff.register_backend("codediff", {
 
 		diff_two_changes(opts.left, opts.right)
 	end,
+
+	diff_history_revisions = function(opts)
+		if not utils.has_dependency("codediff") then
+			return
+		end
+
+		diff_two_changes_with_history(opts.left, opts.right)
+	end,
 })

lua/jj/diff/diffview.lua

@@ -24,6 +24,21 @@ local function diff_two_changes(left, right)
 	vim.cmd(string.format("DiffviewOpen %s..%s", commit_id_right, commit_id_left))
 end
 
+local function diff_two_changes_with_history(left, right)
+	local commit_id_left = utils.get_commit_id(left)
+	if commit_id_left == nil then
+		return
+	end
+
+	local commit_id_right = utils.get_commit_id(right)
+	if commit_id_right == nil then
+		return
+	end
+
+	-- test
+	vim.cmd(string.format("DiffviewFileHistory --range=%s..%s", commit_id_right, commit_id_left))
+end
+
 -- Register the diffview backend
 diff.register_backend("diffview", {
 	diff_current = function(opts)
@@ -59,4 +74,11 @@ diff.register_backend("diffview", {
 
 		diff_two_changes(opts.left, opts.right)
 	end,
+	diff_history_revisions = function(opts)
+		if not utils.has_dependency("diffview") then
+			return
+		end
+
+		diff_two_changes_with_history(opts.left, opts.right)
+	end,
 })

lua/jj/diff/init.lua

@@ -28,6 +28,7 @@ local utils = require("jj.utils")
 ---@field diff_current? fun(opts: jj.diff.current_opts)
 ---@field show_revision? fun(opts: jj.diff.revision_opts)
 ---@field diff_revisions? fun(opts: jj.diff.revisions_opts)
+---@field diff_history_revisions? fun(opts: jj.diff.revisions_opts)
 
 ---@class jj.diff.config
 ---@field backend? jj.diff.backend
@@ -99,7 +100,7 @@ end
 -----------------------------------------------------------------------
 
 --- Single dispatcher (canonical entry point)
----@param kind "current"|"revision"|"revisions"
+---@param kind "current"|"revision"|"revisions"|"history"
 ---@param opts table
 function M.open(kind, opts)
 	opts = opts or {}
@@ -120,6 +121,10 @@ function M.open(kind, opts)
 			return backend.diff_revisions(opts)
 		end
 		return backends.native.diff_revisions(opts)
+	elseif kind == "history" then
+		if backend.diff_history_revisions then
+			return backend.diff_history_revisions(opts)
+		end
 	else
 		utils.notify("[Diff] unknown diff kind: " .. tostring(kind), vim.log.levels.ERROR)
 	end
@@ -143,6 +148,12 @@ function M.diff_revisions(opts)
 	return M.open("revisions", opts)
 end
 
+-- Diff between two revisions with history mode active
+--- @param opts jj.diff.revisions_opts
+function M.diff_history_revisions(opts)
+	return M.open("history", opts)
+end
+
 ---
 -----------------------------------------------------------------------
 -- BACKWARDS COMPATIBLE API

lua/jj/diff/native.lua

@@ -124,4 +124,10 @@ diff.register_backend("native", {
 		local cmd = string.format("jj diff -f %s -t %s --quiet --no-pager", opts.left, opts.right)
 		terminal.run_floating(cmd, require("jj.cmd").floating_keymaps())
 	end,
+	diff_history_revisions = function(_)
+		utils.notify(
+			"Diffing revisions with history mode is not supported on the `native` backend.",
+			vim.log.levels.WARN
+		)
+	end,
 })