Compare: check for modified file when saving

SmartGit's diff tool is great, and I'll often use it to review and adjust changes before committing. However, SmartGit's editor has some significant limitations, and I'll do much of my work using BBEdit.

At times I'll have the same file open in both SmartGit and BBEdit. If I make a change with SmartGit, and then try to save a different change with BBEdit, BBEdit will warn me that the disk file has been changed. If I've changed a file with BBEdit, though, and then try to save a change with SmartGit, it'll happily tromp over the changed file.

Suggestion: when you're about to save a file, make sure it hasn't changed since it was read. If it has, show a warning.