I have encountered this while translating Mousepad: #: ../mousepad/mousepad-dialogs.c:410 msgid "If you don't save the document, all the external changes will be lost." Somehow I think it should be the other way around: msgid "If you save the document, all the external changes will be lost." That's because the dialog seems to be titled "Externally Modified" and the user is also warned: "The document has been externally modified. Do you want to continue saving?" Marked MAJOR because of possible unwanted implications for the user.
Fixed in commit 02594e8, thanks. *** This bug has been marked as a duplicate of bug 8940 ***