Commit 66818712 authored by Glenn Morris's avatar Glenn Morris
Browse files

Add a very basic bisecting guide

parent f05e2ff2
......@@ -267,3 +267,52 @@ For example, on RHEL6 I needed:
yum --enablerepo=epel install python-simpletal
Then point your web-browser to .
* Bisecting
This is a semi-automated way to find the revision that introduced a bug.
First, get the bzr bisect plugin if you do not have it already:
cd ~/.bazaar/plugins
bzr branch lp:bzr-bisect bisect
`bzr help bisect' should work now.
It's probably simplest to make a new copy of the branch to work in
from this point onwards.
Identify the last known "good" revision where the relevant issue is
NOT present (e.g. maybe Emacs 24.1). Let's say this is revision 1000.
bzr bisect start
bzr bisect no -r 1000
At this point, bzr will switch to the mid-point of revision 1000 and
the current revision. If you know that the issue was definitely
present in some specific revision (say 2000), you can use:
bzr bisect yes -r 2000
Now bzr switches to revision 1500.
Now test whether the issue is present. You might need to rebuild
Emacs to do this, or if you know the problem is in a specific Lisp
file, you might be able to get away with just loading that one file in
current Emacs.
If the issue is present, use
bzr bisect yes
If it is not, use
bzr bisect no
Repeat until you zero-in on the specific revision.
When finished, use
bzr bisect reset
or simply delete the entire branch if you created it just for this.
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