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Browsing history

bzr log

The bzr log command shows a list of previous revisions.

As with bzr diff, bzr log supports the -r argument:

% bzr log -r 1000..          # Revision 1000 and everything after it
% bzr log -r ..1000          # Everything up to and including r1000
% bzr log -r 1000..1100      # changes from 1000 to 1100
% bzr log -r 1000            # The changes in only revision 1000

Viewing merged revisions

As distributed VCS tools like Bazaar make merging much easier than it is in central VCS tools, the history of a branch may often contain lines of development splitting off the mainline and merging back in at a later time. Technically, the relationship between the numerous revision nodes is known as a Directed Acyclic Graph or DAG for short.

In many cases, you typically want to see the mainline first and drill down from there. The default behaviour of log is therefore to show the mainline and indicate which revisions have nested merged revisions. To explore the merged revisions for revision X, use the following command:

bzr log -n0 -rX

To see all revisions and all their merged revisions:

bzr log -n0

Note that the -n option is used to indicate the number of levels to display where 0 means all. If that is too noisy, you can easily adjust the number to only view down so far. For example, if your project is structured with a top level gatekeeper merging changes from team gatekeepers, bzr log shows what the top level gatekeeper did while bzr log -n2 shows what the team gatekeepers did. In the vast majority of cases though, -n0 is fine.

Tuning the output

The log command has several options that are useful for tuning the output. These include:

  • --forward presents the log in chronological order, i.e. the most recent revisions are displayed last.
  • the --limit option controls the maximum number of revisions displayed.

See the online help for the log command or the User Reference for more information on tuning the output.

Viewing the history for a file

It is often useful to filter the history so that it only applies to a given file. To do this, provide the filename to the log command like this:

bzr log foo.py

Viewing an old version of a file

To get the contents of a file at a given version, use the cat command like this:

bzr cat -r X file

where X is the revision identifier and file is the filename. This will send output to the standard output stream so you’ll typically want to pipe the output through a viewing tool (like less or more) or redirect it like this:

bzr cat -r -2 foo.py | less
bzr cat -r 1 foo.py > /tmp/foo-1st-version.py

Graphical history viewers

History browsing is one area where GUI tools really make life easier. Bazaar has numerous plug-ins that provide this capability including QBzr and bzr-gtk. See Using plugins for details on how to install these if they are not already installed.

To use the graphical viewer from QBzr:

bzr qlog

To use the graphical viewer from bzr-gtk:

bzr viz

viz is actually a built-in alias for visualize so use the longer command name if you prefer.