sage: Determine SAGE_LOCAL, SAGE_ROOT via sage-config if it exists

[mkoeppe]

We reduce the runtime dependency of sage on sage-env-config.

We query sage-config (installed by sage_conf, which has a dependency on our python3 package) for the values of SAGE_LOCAL and SAGE_ROOT. sage-config must be in the same directory as $0.

This allows the installed sage script to be invoked directly from $SAGE_LOCAL/bin in an environment without SAGE_... variables, restoring what was previously implemented in #25486.

Also, we move sourcing of sage-env-config (but not sage-env!) earlier in the sage script.
This is so that commands such as $SAGE_LOCAL/bin/sage --root work correctly.

Follow-up tickets:

• Make $SAGE_LOCAL/bin/sage work again from any directory, in an environment without SAGE_* variables, following symlinks #30888 resolve symlinks so it even works for symlinks to $SAGE_LOCAL/bin/sage
• src/bin/sage-env: Make sure $SAGE_VENV/bin is at the beginning of the PATH #30013 set SAGE_VENV too
• remove the build-time dependency of the sage distribution on src/bin/sage-env-config

CC: @kiwifb @orlitzky @jhpalmieri @antonio-rojas @seblabbe

Component: build

Keywords: sd111

Author: Matthias Koeppe

Branch/Commit: eb3793e

Reviewer: Dima Pasechnik, François Bissey

Issue created by migration from https://trac.sagemath.org/ticket/29852

[mkoeppe]

Changed dependencies from #29825 to #29850

[mkoeppe]

Changed dependencies from #29850 to #22731

[mkoeppe]

Branch: u/mkoeppe/get_rid_of_sage_env_config

[mkoeppe]

Author: Matthias Koeppe

[mkoeppe]

Last 10 new commits:

8f88709	src/bin/sage: Only source sage-env-config if it exists
ab2655e	src/bin/sage: Use python3 etc. from PATH instead of using SAGE_LOCAL
4577f37	src/bin/sage-env: Make sage-env-config optional
c35c170	sage.env: Add SAGE_VENV
c585d94	src/sage: Replace some SAGE_LOCAL by SAGE_VENV
2fd195f	src/bin/sage: Fix reference to trac ticket
f3b7a9c	src/sage/env.py: Add documentation
995af9f	Merge branch 't/22731/22731' into t/29852/get_rid_of_sage_env_config
2bce7b8	src/bin/sage: Find SAGE_ROOT, SAGE_LOCAL from sage-config
9810f49	src/bin/sage: Determine SAGE_ROOT, SAGE_LOCAL earlier

[mkoeppe]

Commit: 9810f49

[dimpase]

comment:10

lgtm

[dimpase]

Reviewer: Dima Pasechnik

[mkoeppe]

comment:11

Thanks!

[vbraun]

Changed branch from u/mkoeppe/get_rid_of_sage_env_config to 9810f49

[vbraun]

Changed branch from 9810f49 to u/mkoeppe/get_rid_of_sage_env_config

[sagetrac-git]

Changed commit from 9810f49 to eb3793e

[sagetrac-git]

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

1fe77a8	src/bin/sage-env: Do not set SAGE_SCRIPTS_DIR
eb3793e	Merge branch 't/22731/22731' into t/29852/get_rid_of_sage_env_config

[mkoeppe]

comment:16

Merged the updated #22731 - needs another round of review

[mkoeppe]

Changed keywords from none to sd111

[mkoeppe]

comment:17

Hoping we can make progress on this ticket this week - https://wiki.sagemath.org/days111

[mkoeppe]

Changed dependencies from #22731 to none

[mkoeppe]

comment:20

Finishing the review of this ticket would be helpful - #30888 and #30013 depend on it.

[kiwifb]

Changed reviewer from Dima Pasechnik to Dima Pasechnik, François Bissey

[kiwifb]

comment:21

I was rather convinced that was already in. Oh yes, it has been reverted once. It should be fine now.

[mkoeppe]

comment:22

Thank you!

[vbraun]

Changed branch from u/mkoeppe/get_rid_of_sage_env_config to eb3793e