When renaming/moving a file, git log /path/to/file will only show the commits history from that renaming/moving until now. To follow the commits until the first one and display them in the history you will need to do a
git log --follow /path/to/file
All the commits will be shown in the history. But note that this will work only for a single file.
If you’re using Egit in Eclipse, you can do the same by checking the box Follow Renames in Preferences -> Team -> Git -> History
PS: If you want to move a file in a git repository, you can consider using git mv oldpath newpath which is a shorthand for
mv oldpath newpath git add newpath git rm oldpath
More informations and options for git log.