How to figure out what revision number causes a bug

Something worked. And now it doesn't. This is called a regression.

This happens. Most commits fix/improve things, but every once in a while, something breaks. Sometimes, by fixing a bug, we introduce another. Tiki has so many features that it's difficult to test everything. Lots of eyeballs and good bug reporting is essential

You'd like to report the bug and inform the right person. But how to figure out who introduced the problem and when?

You can use SVN-bisect or the manual procedure below.

1. You should subscribe to SVN mailing list to be informed of all fixes and to search in your mail client
   • This is a high-volume list so you may want to put a filter to store messages in a directory
2. Get Tiki via SVN (choose your branch)
3. Check your version number.
   
   svn info

   $ svn info
   Path: .
   URL: https://tikiwiki.svn.sourceforge.net/svnroot/tikiwiki/branches/7.x
   Repository Root: https://tikiwiki.svn.sourceforge.net/svnroot/tikiwiki
   Repository UUID: b456876b-0849-0410-b77d-98878d47e9d5
   Revision: 34719
   Node Kind: directory
   Schedule: normal
   Last Changed Author: jonnybradley
   Last Changed Rev: 34716
   Last Changed Date: 2011-05-31 10:42:10 -0700 (Tue, 31 May 2011)

   
   
   
4. Update SVN to a specific revision which you know works.
   To update your source to a specific revision, use:
   
   Updating to revision 34715

   [demotw@alpha 7x]$ svn update -r 34715
   U    lib/categories/categlib.php
   U    templates/categobjects_title.tpl
   U    templates/categobjects.tpl
   
   Fetching external item into 'lib/adodb'
   Updated external to revision 34668.
   
   Fetching external item into 'lib/smarty'
   Updated external to revision 34668.
   
   Fetching external item into 'lib/jscalendar'
   Updated external to revision 34668.
   
   Fetching external item into 'lib/htmlpurifier'
   Updated external to revision 34668.
   
   Fetching external item into 'lib/pclzip'
   Updated external to revision 34668.
   
   Fetching external item into 'lib/jquery'
   
   Fetching external item into 'lib/jquery/jquery.s5'
   Updated external to revision 41.
   
   Fetching external item into 'lib/jquery/jquery.sheet'
   
   Fetching external item into 'lib/jquery/jquery.sheet/jquery-ui/ui'
   Updated external to revision 4075.
   
   Fetching external item into 'lib/jquery/jquery.sheet/jquery-ui/theme'
   Updated external to revision 4075.
   
   Updated to revision 405.
   Updated to revision 34668.
   
   Fetching external item into 'lib/phpcas'
   Updated external to revision 23921.
   
   Fetching external item into 'lib/ezcomponents'
   Updated external to revision 34668.
   
   Fetching external item into 'lib/ckeditor'
   Updated external to revision 34668.
   
   Fetching external item into 'lib/codemirror'
   Updated external to revision 34668.
   
   Fetching external item into 'lib/svg-edit'
   Updated external to revision 2034.
   
   Fetching external item into 'lib/mobileesp'
   Updated external to revision 34668.
   
   Fetching external item into 'lib/html5shim'
   Updated external to revision 34668.
   
   Fetching external item into 'lib/pear/Text'
   Updated external to revision 34720.
   
   Fetching external item into 'lib/core/Zend'
   Updated external to revision 24101.
   
   Updated to revision 34715.
   [demotw@alpha 7x]$

   
   
   
5. Clear all caches by visiting tiki-admin_system.php?do=all
6. Test to confirm the bug is not present
7. Update SVN to a specific revision which you know doesn't work.
8. Test to confirm the bug is present
9. Repeat by changing revision number back & forth until you can pinpoint the revision which introduces the issue.
   
   Since you may have quite a few trial and errors, you may want to ignore externals, but an issue can be caused by an external...

   svn update --ignore-externals -r 34750

10. Reply to the message on the SVN mailing list to specify what issue this commit is introducing.

Note: Database structure changes between version, so you may see bugs/error messages because of this. However, most of the time, it won't prevent you to use this method to pinpoint the problematic commit.

Related

• http://www.selenic.com/mercurial/hg.1.html#bisect
• https://launchpad.net/bzr-bisect