Index: bsd.port.mk
===================================================================
--- bsd.port.mk
+++ bsd.port.mk
@@ -1176,22 +1176,48 @@
 
 .else
 
-# Look for ${PATCH_WRKSRC}/.../*.orig files, and (re-)create
-# ${FILEDIR}/patch-* files from them.
+# Look for files named "*.orig" under ${PATCH_WRKSRC} and (re-)generate
+# ${FILEDIR}/patch-* files from them.  By default, '-' (dash, minus) is
+# used to replace path separators in patch file names; it can be set to
+# something else via PATCH_PATH_SEPARATOR variable (note that only [-+_]
+# characters are allowed).
+#
+# If a file name happens to contain character which is also a separator
+# replacement character, it will be doubled in the resulting patch name.
+#
+# To minimize gratuitous patch renames, newly generated patches will be
+# written under existing file names if they use any of the allowed path
+# separators ([-+_]) or legacy double underscore (__).
 
 .if !target(makepatch)
+PATCH_PATH_SEPARATOR?=	-
 makepatch:
+.if empty(PATCH_PATH_SEPARATOR) || ${PATCH_PATH_SEPARATOR:C/[-+_]//}
+	@${ECHO_MSG} "Error (${.TARGET}): PATCH_PATH_SEPARATOR must be one of the [-+_] characters."
+	@${FALSE}
+.endif
 	@${MKDIR} ${FILESDIR}
 	@(cd ${PATCH_WRKSRC}; \
-		for i in `find . -type f -name '*.orig'`; do \
-			ORG=$$i; \
-			NEW=$${i%.orig}; \
-			cmp -s $${ORG} $${NEW} && continue; \
-			OUT=${FILESDIR}`${ECHO} $${NEW} | \
-				${SED} -e 's|/|__|g' \
-					-e 's|^\.__|/patch-|'`; \
-			${ECHO} ${DIFF} -ud $${ORG} $${NEW} '>' $${OUT}; \
-			${DIFF} -ud $${ORG} $${NEW} > $${OUT} || ${TRUE}; \
+		for f in `${FIND} -s . -type f -name '*.orig'`; do \
+			ORIG=$${f#./}; \
+			NEW=$${ORIG%.orig}; \
+			cmp -s $${ORIG} $${NEW} && continue; \
+			! for _lps in `${ECHO} _ - + | ${SED} -e \
+				's|${PATCH_PATH_SEPARATOR}|__|'`; do \
+					PATCH=`${ECHO} $${NEW} | ${SED} -e "s|/|$${_lps}|g"`; \
+					test -f "${FILESDIR}/patch-$${PATCH}" && break; \
+			done || ${ECHO} $${_SEEN} | ${GREP} -q /$${PATCH} && { \
+				PATCH=`${ECHO} $${NEW} | ${SED} -e \
+					's|${PATCH_PATH_SEPARATOR}|&&|g' -e \
+					's|/|${PATCH_PATH_SEPARATOR}|g'`; \
+				_SEEN=$${_SEEN}/$${PATCH}; \
+			}; \
+			OUT=${FILESDIR}/patch-$${PATCH}; \
+			${ECHO} ${DIFF} -udp $${ORIG} $${NEW} '>' $${OUT}; \
+			TZ=UTC ${DIFF} -udp $${ORIG} $${NEW} | ${SED} -e \
+				'/^---/s|\.[0-9]* +0000$$| UTC|' -e \
+				'/^+++/s|\([[:blank:]][-0-9:.+]*\)*$$||' \
+					> $${OUT} || ${TRUE}; \
 		done \
 	)
 .endif