Re: Master and origin/master diverged

On 22 June 2012 16:47, Neal Kreitzinger [off-list ref] wrote:

On 6/22/2012 3:18 PM, Hilco Wijbenga wrote:

quoted

On 22 June 2012 12:01, Neal Kreitzinger [off-list ref] wrote:

quoted

On 6/22/2012 12:53 PM, Hilco Wijbenga wrote:

quoted

One of my developers managed to push something that somehow "diverged"
origin/master from everyone else's local master.

A --> B --> C --> D (everybody's local master)
|
\--> B' --> C' --> D' --> E (origin/master)

(i.e., A is the commit where things diverged; everyone's local master
points to D but the new commit (E) that was pushed to origin/master
uses different SHA1s for B, C, and D)...


Now running git pull creates a merge commit joining D and E.

...Does anyone have any idea as to what might have happened? Perhaps if
I

understand how this happened I might be able to prevent it from
happening again.

Some ways you can prevent it from happening again:

quoted

(2) have your devs do git pull --ff-only

Is this something that can be set in git config? I looked but didn't
see anything obvious.

OTTOMH, you could change the git fetch config for master and take away the
leading '+' sign which would not allow non-fastforward fetches of master.
 That in turn would prevent merging such a non-ff remote tracking branch of
master into your branch master.


Actually, I guess what I really want is

quoted

something for git push, right?

Some ways to do it:
(1) I think you could have rebase and commit hooks locally that prevent
someone from rewriting history on master.  That in turn would prevent
someone from pushing a rewritten history.

Yes, I have been thinking about that.

How does one create "portable" hooks? I have to deal with GNU/Linux,
OS X, and MS Windows. We all have Java installed so I first thought of
using JGit but I am not clear on how well JGit supports using it in a
hooks. Should I make Ruby a required part of the dev environment and
use Ruby hooks?

(2) When merging topic branches to master use git merge --ff-only.  Then
when you push it to remote master you know it's a fastforward and not a
history rewrite.

Given how hard it is to teach devs to only push fast-forward merges, I
am not sure how well this would work.