Allow using Sage without dev/git

[vbraun]

For binary builds / system-wide installs and perhaps tarballs we should not require the git repository. This ticket fixes two doctests for that use case.

That is, to remove the development functionality you can now

• delete SAGE_SRC/sage/dev
• delete SAGE_ROOT/.git
  and all doctests still pass

Depends on #14482

Component: misc

Author: Volker Braun

Branch/Commit: u/vbraun/run_without_git @ 24e5a73

Reviewer: R. Andrew Ohana

Issue created by migration from https://trac.sagemath.org/ticket/15465

[vbraun]

Branch: u/vbraun/run_without_git

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

[067dfc6](https://github.com/sagemath/sagetrac-mirror/commit/067dfc6)	Relax the cmdline test of "sage -dev", it may be disabled
[fa29095](https://github.com/sagemath/sagetrac-mirror/commit/fa29095)	Merging latest dev scripts to avoid conflict in sage-dev
[713737f](https://github.com/sagemath/sagetrac-mirror/commit/713737f)	fall back to doctesting all files if new files cannot be identified
[946b5b4](https://github.com/sagemath/sagetrac-mirror/commit/946b5b4)	fix the commandline sage -dev script
[2941308](https://github.com/sagemath/sagetrac-mirror/commit/2941308)	Use a DoctestSageDevWrapper for the global dev object during doctests
[6a512d6](https://github.com/sagemath/sagetrac-mirror/commit/6a512d6)	Explicitly specify the key type in ssh-keygen (requried for Sun SSH)
[702d7af](https://github.com/sagemath/sagetrac-mirror/commit/702d7af)	do not suggest force push

[sagetrac-git]

Commit: 067dfc6

[vbraun]

Dependencies: #14482

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

[24e5a73](https://github.com/sagemath/sagetrac-mirror/commit/24e5a73)

better to ask for forgiveness

[sagetrac-git]

Changed commit from 067dfc6 to 24e5a73

[ohanar]

comment:5

Because of the lazy import of the dev object, asking for forgiveness won't work.

[ohanar]

Reviewer: R. Andrew Ohana