fix: make urls relative before calling Sbrowse

Summary:

When you are in a buffer that has a absolute path as its name. When calling
Sbrowse it will use that hole path in the url. This is obviously incorrect.

Now we are making sure we get the relative path before we create the url so we
don't end up going to a 404.

Test Plan:

CI, unit tests. I have also had the change locally for quite some time.

.luacheckrc

@@ -7,4 +7,4 @@ codes = true
 self = false
 
 -- Global objects defined by the C code
-read_globals = { "vim", "describe", "it", "assert", "teardown" }
+read_globals = { "vim", "describe", "it", "assert", "teardown", "spy", "stub", "before_each" }

lua/sapling_scm_tests/remote_url_spec.lua

@@ -92,3 +92,19 @@ describe("sapling_scm.remote_url.commit", function()
     )
   end)
 end)
+
+describe("remote url integration test", function()
+  local un_stubbed = vim.cmd
+  local match = require "luassert.match"
+
+  before_each(function()
+    vim.cmd("edit " .. os.getenv "PWD" .. "/.github/workflows/test.yml")
+
+    stub(vim, "cmd")
+    un_stubbed "Sbrowse"
+  end)
+
+  it("creates the url from a relative path when the buffer is absolute", function()
+    assert.spy(vim.cmd).was_called_with(match.has_match "/blob/[^/]+/.github/workflows/test.yml")
+  end)
+end)

lua/sapling_scm_tests/setup.lua

@@ -4,3 +4,6 @@ _G.describe = busted.describe
 _G.it = busted.it
 _G.assert = busted.assert
 _G.teardown = busted.teardown
+_G.spy = busted.spy
+_G.stub = busted.stub
+_G.before_each = busted.before_each

plugin/sapling_scm.lua

@@ -71,7 +71,7 @@ else
 end
 
 vim.api.nvim_create_user_command("Sbrowse", function(props)
-  local file = vim.fn.expand "%"
+  local file = vim.fn.expand "%:."
   local start_line = props.line1
   local end_line = props.line2