[source-date-epoch-spec] 04/05: Drop the prohibition on overwriting altogether, but document implementation complexities

[Ximin Luo]

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infinity0 pushed a commit to branch pu/1.1
in repository source-date-epoch-spec.

commit 01174a1cbaf02c8240f9edbfceb57091f8c21575
Author: Ximin Luo <infinity0 at debian.org>
Date:   Mon Nov 13 17:04:23 2017 +0100

    Drop the prohibition on overwriting altogether, but document implementation complexities
---
 source-date-epoch-spec.xml | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/source-date-epoch-spec.xml b/source-date-epoch-spec.xml
index 4ef5be1..81a08a7 100644
--- a/source-date-epoch-spec.xml
+++ b/source-date-epoch-spec.xml
@@ -9,8 +9,9 @@
 			<revnumber>1.1</revnumber>
 			<date>18 October 2017</date>
 			<revremark>
-				Slightly relax prohibition of overwriting the environment variable.
 				Document timestamp clamping.
+				Drop prohibition of overwriting the variable, and instead
+				specify more tightly how to set it.
 			</revremark>
 		</revision>
 		<revision>
@@ -163,9 +164,8 @@
 			This is often called "timestamp clamping".
 		</para>
 		<para>
-			Build processes MUST NOT unset this variable for child
-			processes if it is already present, or overwrite it with
-			a lower (less recent) value.
+			Build processes MUST NOT discriminately unset this
+			variable for child processes if it is already present.
 		</para>
 		<para>
 			Formatting MUST be deferred until runtime if an end
@@ -195,6 +195,12 @@
 			it is recommended to also update source file timestamps to this
 			value, or else this may interact badly with any timestamp clamping.
 		</para>
+		<para>
+			Though it is not forbidden to set <envar>SOURCE_DATE_EPOCH</envar>
+			several times during a build, such as for different child modules,
+			build processes doing this should ensure that the differing values
+			do not interfere with each other in a nondeterministic way.
+		</para>
 	</sect2>
 	<sect2>
 		<title>Timestamp clamping</title>

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