Clarify use of the "today" Sphinx variable

Add a comment explaining the purpose of setting the "today" variable in
Sphinx invocations to prevent confusion caused by the absence of that
variable from reStructuredText sources.

(cherry picked from commit e67cdb390a73341802da1deed57254276a294be5)

diff --git a/doc/arm/Makefile.in b/doc/arm/Makefile.in
index 146f157813606f4268ef5b009db6919dc8dffce4..74480da2cf2facb6cd2c5f4d4040b2fe23238904 100644 (file)
--- a/doc/arm/Makefile.in
+++ b/doc/arm/Makefile.in
@@ -32,6 +32,8 @@ common_SPHINXOPTS =   \
        -v              \
        -c "${abs_srcdir}"
 
+# The "today" variable set below is not directly used in the ARM, but its value
+# is implicitly inserted on the title page of the PDF file produced by Sphinx.
 ALLSPHINXOPTS =                                \
        $(common_SPHINXOPTS)                    \
        -D today="${RELEASE_DATE}"              \