A ChangeLog is a file (usually called `ChangeLog') which keeps a log of all changes you have made to the files in its directory. For example, the `src/ChangeLog' file for Jade keeps a list of changes made to the editor's source code.
There is no magic involved, you simply use a command to add a new entry to a directory's log after modifying a file in that directory. You then have to enter a summary of the changes that you made.
The command to do this is,
If you enter more than one change in the same day (and from the same host) the same heading will be used. The heading consists of the time and date, your name, your login and the name of the host you're on. (5)
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