Re: "git bisect run make" adequate to locate first unbuildable commit?

From: Philip Oakley <philipoakley@iee.org>
Date: Feb 9, 2018, 22:44 UTC
Message-ID: <7135CFE5288C49EEA02785C1F407B46D@PhilipOakley>
In-Reply-To: <alpine.LFD.2.21.1802091553290.17104@localhost.localdomain>

From: "Robert P. J. Day" <rpjday@crashcourse.ca>

> On Fri, 9 Feb 2018, Philip Oakley, CEng MIET wrote:

(apologies for using the fancy letters after the name ID...)

Show 26 quoted lines

>
>> From: "Robert P. J. Day" <rpjday@crashcourse.ca>
>> >
>> > writing a short tutorial on "git bisect" and, all the details of
>> > special exit code 125 aside, if one wanted to locate the first
>> > unbuildable commit, would it be sufficient to just run?
>> >
>> >  $ git bisect run make
>> >
>> > as i read it, make returns either 0, 1 or 2 so there doesn't appear
>> > to be any possibility of weirdness with clashing with a 125 exit code.
>> > am i overlooking some subtle detail here i should be aware of? thanks.
>> >
>> > rday
>>
>> In the spirit of pedanticism, one should also clarify the word
>> "first", in that it's not a linear search for _an_ unbuildable
>> commit, but that one is looking for the transition between an
>> unbroken sequence of unbuildable commits, which transitions to
>> buildable commits, and its the transition that is sought. (there
>> could be many random unbuildable commits within a sequence in some
>> folks' processes!)
>
>  quite so, i should have been more precise.
>
> rday

The other two things that may be happening (in the wider bisect discussion) 
that I've heard of are:
1. there may be feature branches that bypass the known good starting commit, 
which can cause understanding issues as those side branches that predate the 
start point are also considered potential bu commits.
2. if you just want the first parent check for the bad commit point, that 
mark the second parents of merges as being good.

Also, I'd expect that the skipped commits aren't 'counted' (too hard?) for the bisect algorithm's reporting.

https://stackoverflow.com/questions/5638211/how-do-you-get-git-bisect-to-ignore-merged-branches contains a number of the ideas..

Philip