40 lines
1.4 KiB
Diff
40 lines
1.4 KiB
Diff
From 41843856d1f09c8fe718630a6fa4318441c7be38 Mon Sep 17 00:00:00 2001
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From: Evan Goode <mail@evangoo.de>
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Date: Mon, 16 Oct 2023 18:44:53 +0000
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Subject: [PATCH 04/11] Document shell-like parameter expansion for variables
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=changelog=
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msg: Support ${parameter:-word} and ${parameter:+word} parameter expansion in variables
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type: enhancement
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resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1789346
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---
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doc/conf_ref.rst | 12 ++++++++++++
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1 file changed, 12 insertions(+)
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diff --git a/doc/conf_ref.rst b/doc/conf_ref.rst
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index 9397f0008..fdb34323c 100644
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--- a/doc/conf_ref.rst
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+++ b/doc/conf_ref.rst
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@@ -829,6 +829,18 @@ Although users are encouraged to use named variables, the numbered environmental
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[myrepo]
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baseurl=https://example.site/pub/fedora/$DNF1/releases/$releasever
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+A limited form of shell-like parameter expansion is supported for variables.
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+
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+``${my_variable:-word}`` If ``my_variable`` is unset or empty, then ``word`` will be substituted. Otherwise, the value of ``my_variable`` will be substituted.
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+
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+``${my_variable:+word}`` If ``my_variable`` is set and not empty, then ``word`` will be substituted. Otherwise, the empty string will be substituted.
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+
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+Parameter expansions can be nested up to a maximum depth of 32. For example::
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+
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+ ${my_defined_variable:+${my_undefined_variable:-foobar}}
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+
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+will evaluate to ``foobar``.
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+
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.. _conf_main_and_repo_options-label:
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--
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2.49.0
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