11/17: refcard: Add section on "guix time-machine".

[Ricardo Wurmus]

rekado pushed a commit to branch master
in repository maintenance.

commit 5b547fb52559c4640c09320d6eae9845eccbe2c6
Author: Ricardo Wurmus <rekado@elephly.net>
AuthorDate: Mon May 30 13:33:25 2022 +0200

    refcard: Add section on "guix time-machine".
---
 doc/refcard/guix-refcard.lout | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/doc/refcard/guix-refcard.lout b/doc/refcard/guix-refcard.lout
index 588f8a5..ff81a5a 100644
--- a/doc/refcard/guix-refcard.lout
+++ b/doc/refcard/guix-refcard.lout
@@ -139,6 +139,17 @@ from a user-supplied file that looks like this:
 }
 @End @Category
 
+@C { Using a Different Version of Guix }
+@Begin
+@LP
+The @F{ guix time-machine } command provides access to other revisions of
+Guix, for example to install older versions of packages, or to reproduce
+a computation in an identical environment.
+
+@LP
+@LEntry {  guix time-machine -C @Var { file } "--" @Var { commands @Dots }  }
+{ Run @Var{ commands } in a version of Guix specified by the given channels in 
@Var { file } }
+@End @Category
 
 @NP
 @C { Customizing Packages }