Tuesday 7 January 2014

How to update a forked GitHub repo (in this case tm-sme/Lib_Vulnerabilities)

Today I helped to update the tm-sme/Lib_Vulnerabilities repo which is a fork of the TMContent/Lib_Vulnerabilities and is being auto-updated in real-time when changes made to the https://sme.teammentor.net/ server (i.e every time there is a content change in https://sme.teammentor.net there is a server-side git commit, followed by a git pull to tm-sme/Lib_Vulnerabilities (which is a pretty sweet workflow))

The issue we had was how to push the changes from tm-sme/Lib_Vulnerabilities into the TMContent/Lib_Vulnerabilities  repo, so that they can be synced back to https://vulnerabilities.teammentor.net

Note: this workflow would had been easier if the two repos where in sync, but it happened that there was one commit made to TMContent/Lib_Vulnerabilities (which is the master repo) on the 13th of Dec (d26f385) in between a bunch of updates to the tm-sme/Lib_Vulnerabilities repo (done automatically by TeamMentor). Bottom line: at this stage the repos are not compatible, which is why the GitHub Pull Requests don't work.

Here are the Git commands I executed locally to merge these repos successfully:

Step 1) Clone repo and try to do a simple pull

1) git plugin$ git clone git@github.com:tm-sme/Lib_Vulnerabilities.git
2) cd Lib_Vulnerabilities/
3) git remote add upstream git@github.com:TMContent/Lib_Vulnerabilities.git
4) git checkout -b mergeBranch
5) git pull upstream master:mergeBranch

    which doesn't work:
        ! [rejected]        master     -> mergeBranch  (non-fast-forward)

Step 2) Create a local (forced) copy of the main repo and do the merge locally

6) git checkout -b upstreamVersion
7) git pull -f upstream master:upstreamVersion
8) git checkout mergeBranch
9) git merge upstreamVersion

    which works:
        Merge made by the 'recursive' strategy.
        LICENSE.TXT | 50 ++++++++++++++++++++++++++++++++++++++++++
        1 file changed, 50 insertions(+)
        create mode 100644 LICENSE.TXT

Step 3) push the merged files to both repos

10) git push origin mergeBranch:mergeBranch
        Counting objects: 7, done.
        Delta compression using up to 4 threads.
        Compressing objects: 100% (5/5), done.
        Writing objects: 100% (5/5), 3.99 KiB | 0 bytes/s, done.
        Total 5 (delta 2), reused 0 (delta 0)
        To git@github.com:tm-sme/Lib_Vulnerabilities.git
         * [new branch]      mergeBranch -> mergeBranch

11) push upstream mergeBranch:mergeBranch

        Counting objects: 2971, done.
        Delta compression using up to 4 threads.
        Compressing objects: 100% (774/774), done.
        Writing objects: 100% (2890/2890), 431.68 KiB | 0 bytes/s, done.
        Total 2890 (delta 2199), reused 2801 (delta 2116)
        To git@github.com:TMContent/Lib_Vulnerabilities.git
         * [new branch]      mergeBranch -> mergeBranch

Step 4) merge into main branch of main repo

12) ... the next step was done on GitHub using a Pull Request on the TMContent/Lib_Vulnerabilities  repo

       git push upstream mergeBranch:master

Step 5) update local master and forked repo master

13) git checkout master
14) git pull upstream master:master
15) git push origin master:master

Here is what the main repo looks after the merge