Add support for a "sagerc" script

[jdemeyer]

This deals with adding support for a file

$DOT_SAGE/sagerc

which will be sourced after sage-env, so it can be used to override the environment variables used in Sage.

Apply:

1. attachment: 12647_sagerc.patch to SAGE_ROOT.
2. attachment: 12647_sagerc_doc.patch, attachment: trac_12647-review.patch to the Sage library.

Component: scripts

Author: Jeroen Demeyer

Reviewer: John Palmieri

Merged: sage-5.0.beta9

Issue created by migration from https://trac.sagemath.org/ticket/12647

[jdemeyer]

comment:1

This still needs a documentation patch.

[jdemeyer]

Author: Jeroen Demeyer

[jhpalmieri]

comment:2

Where do you suggest adding documentation? The reference manual (here or here, perhaps)? The top-level README.txt?

[jdemeyer]

comment:3

Attachment: 12647_sagerc_doc.patch.gz

[jdemeyer]

Description changed:

--- 
+++ 
@@ -4,3 +4,7 @@
 $DOT_SAGE/sagerc
 ```
 which will be sourced after `sage-env`, so it can be used to override the environment variables used in Sage.
+
+**Apply**:
+1. [attachment: 12647_sagerc.patch](https://github.com/sagemath/sage-prod/files/10655058/12647_sagerc.patch.gz) to `SAGE_ROOT`.
+2. [attachment: 12647_sagerc_doc.patch](https://github.com/sagemath/sage-prod/files/10655056/12647_sagerc_doc.patch.gz) to the Sage library.

[jdemeyer]

comment:4

Replying to @jhpalmieri:

Where do you suggest adding documentation? The reference manual (here or here, perhaps)? The top-level README.txt?

I created a new file in the reference manual mentioning sagerc and init.sage.

[jhpalmieri]

Reviewer: John Palmieri

[jhpalmieri]

comment:5

In a line like

if [ "$SAGE_RC_FILE" = "" ]; then

is there any advantage to replacing the test with [ -z "$SAGE_RC_FILE" ]? (I guess you did it the way you did for consistency with other parts of the script?)

See the review patch for two minor changes to the documentation.

Otherwise, positive review.

[jhpalmieri]

Description changed:

--- 
+++ 
@@ -7,4 +7,4 @@
 
 **Apply**:
 1. [attachment: 12647_sagerc.patch](https://github.com/sagemath/sage-prod/files/10655058/12647_sagerc.patch.gz) to `SAGE_ROOT`.
-2. [attachment: 12647_sagerc_doc.patch](https://github.com/sagemath/sage-prod/files/10655056/12647_sagerc_doc.patch.gz) to the Sage library.
+2. [attachment: 12647_sagerc_doc.patch](https://github.com/sagemath/sage-prod/files/10655056/12647_sagerc_doc.patch.gz), [attachment: trac_12647-review.patch](https://github.com/sagemath/sage-prod/files/10655057/trac_12647-review.patch.gz) to the Sage library.