Add doc to build when ony changelog change

build/debian/README.howto

@@ -226,7 +226,7 @@ http://packages.qa.debian.org/t/tcpdf.html
 
 ##### Create/Maintain dolibarr package
 
-To update dolibarr debian package
+To update dolibarr debian package when upstream version has changed
 
 * You can git clone debian git repo
 > git clone git.debian.org:/git/collab-maint/dolibarr.git [dolibarr-debian]
@@ -270,6 +270,15 @@ Then check/modify also the user/date signature:
 - Date must have format reported by "date -R"
 - Name and email must match value into debian/control file (Entry added here is used by next step).
 
+
+To update dolibarr debian package when only files into debian has changed
+
+* Change files and commit.
+* Add a tag debian/x.y.z+dfsgw-2 (increase the last 1 into 2)
+
+
+Once files has been prepared, it's time to test:
+
 * Try to build package
 > rm -fr ../build-area; git-buildpackage -us -uc
 
@@ -288,6 +297,7 @@ Note: If there was errors managed manually, you may need to make a git commit bu
 > git-buildpackage --git-tag-only --git-retag
 > git push --tags
 
+
 * Compilation is then done by a debian developer and sent
 > sbuild ...
 > dput ...