= Trac Changeset Module =
[[TracGuideToc]]

Trac has a built-in functionality for visualizing ?diffs? - changes to files.

There are different kinds of ''change sets''. 
Some can correspond to revisions made in the repositories,
others can aggregate changes made in several revisions, 
but in the end, any kind of differences could be shown.

The changeset view consists of two parts, the ''header'' 
and the ''diff views''.

== Changeset Header ==

The header shows an overview of the whole changeset.
Here you will find information such as:

 * Timestamp -- When the changeset was commited
 * Author -- Who commited the changeset
 * Message -- A brief description from the author (the commit log message)
 * Files -- A list of files affected by this changeset

If more than one revision is involved in the set of changes being
displayed, the ''Timestamp'', ''Author'' and ''Message'' fields 
won't be shown.

In front of each listed file, you'll find  a colored rectangle. The color
indicates how the file is affected by the changeset.
 
 * Green: Added
 * Red: Removed
 * Yellow: Modified
 * Blue: Copied
 * Gray: Moved

The color legend is located below the header as a reminder.

== Diff Views ==

Below the header is the main part of the changeset, the diff view. Each file is shown in a separate section, each of which will contain only the regions of the file that are affected by the changeset. There are two different styles of displaying the diffs: ''inline'' or ''side-by-side'' (you can switch between those styles using the preferences form):

 * The ''inline'' style shows the changed regions of a file underneath each other. A region removed from the file will be colored red, an added region will be colored green. If a region was modified, the old version is displayed above the new version. Line numbers on the left side indicate the exact position of the change in both the old and the new version of the file.
 * The ''side-by-side'' style shows the old version on the left and the new version on the right (this will typically require more screen width than the inline style.) Added and removed regions will be colored in the same way as with the inline style (green and red, respectively), but modified regions will have a yellow background.

In addition, various advanced options are available in the preferences form for adjusting the display of the diffs:
 * You can set how many lines are displayed before and after every change
   (if the value ''all'' is used, then the full file will be shown)
 * You can toggle whether blank lines, case changes and white space changes are ignored, thereby letting you find the functional changes more quickly


== The Different Ways to Get a Diff ==

=== Examining a Changeset ===

When viewing a repository check-in, such as when following a
changeset [wiki:TracLinks link] or a changeset event in the 
[wiki:TracTimeline timeline], Trac will display the exact changes
made by the check-in.

There will be also navigation links to the ''Previous Changeset''
to and ''Next Changeset''.


'''Note: all of the following will only be available in Trac [milestone:0.10]'''

=== Examining Differences Between Revisions ===

A very frequent need is to look at changes made on a file 
or on a directory spanning multiple revisions. 
The easiest way to get there is from the TracRevisionLog, 
where one can select the '''old''' and the '''new''' revisions
of the path being examined, and then click the ''View changes''
button.

=== Examining Arbitrary Differences ===

One of the main feature of source configuration management
systems is the possibility to work simultaneously on alternate
''Lines of Developments'', or ''branches''. 
The evolution of branches are often made in parallel, making it
sometimes difficult to understand the exact set of differences 
between alternative versions.

This is where Trac comes to the rescue: 
the '''View changes ...''' button in the TracBrowser
leads to a form permitting the selection of arbitrary
''From:'' and ''To:'' path/revision pairs.

The resulting set of differences consist in the changes 
that should be applied to the ''From:'' content in order
to make it look like the ''To:'' content.

For convenience, it is possible to invert the roles
of the '''old''' and the '''new''' path/revision pairs
by clicking the ''Reverse Diff'' link on the changeset page.

=== Checking the Last Change ===

The last possibility for looking at changes is 
to have a quick look on the ''Last Change'' while
browsing a file or a directory. 

This shows the last change that happened on that path.
The links ''Previous Changeset'' and ''Next Changeset''
are replace by links to ''Previous Change'' and ''Next Change'',
which makes it really convenient to traverse the change history
of a specific file or directory.
This view of a changeset, restricted to a specific path,
is called ''restricted changeset''.

Of course, if one is doing that on the root of the
repository, there will be no path restriction
and the full changeset will be shown.


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See also: TracGuide, TracBrowser