I work on mutlirepos and i really dislike gits subtree, subrepo i use https://pypi.org/project/zc.buildout/. Yes i know i can do [1]. But editing on multirepos at the same time i can only do with zc.buildout [2] Still not perfect but it does the job.

[1]

   $ cat req.txt
   requests
   git+ssh://git@gitlab.com/foo/bar/amber.git@0.4.0
   git+ssh://git@gitlab.com/foo/bar/rebam.git@0.4.0

[2]

   $ cat buildout.cfg
   [buildout]
   extends = versions.cfg
   extensions = mr.developer
   auto-checkout = \*
   develop = .
   show-picked-versions = true
   update-versions-file = versions.cfg
   sources-dir = git-sources

   parts = py

   eggs = 
       amber
       rebam
       hammer

   [sources]
   amber = git git@gitlab.com/foo/bar/amber.git@0.4.0
   rebma = git git@gitlab.com/foo/bar/rebma.git@0.4.0

   [py]
   recipe = zc.recipe.egg
   eggs =
       ${buildout:eggs}
   interpreter = py-backend
   dependent-scripts = true