mfikes/how-to-bisect.md

## how-to-bisect.md

      
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              how-to-bisect.md
            
          
    Checkout ClojureScript master and cd to the top of the checkout tree.
Assuming you know it is broken on master but worked in 1.9.562, and there is an easy test you can do right in the REPL.
Run these three commands in your shell:
git bisect start
git bisect bad HEAD
git bisect good r1.9.562

Start up the Node REPL using
script/clean && script/bootstrap && rm -rf .cljs_node_repl && script/noderepljs

Try your test in the REPL and then exit the REPL.
If your test succeeded:
git bisect good

Or if your test failed:
git bisect bad

If the bisect is complete, git will incidate that a certain commit hass "is the first bad commit". Copy all of this text for JIRA.
Otherwise go back to the "Start up the Node REPL" step and repeat until done.
When finished, you can do this to restore your git checkout:
git bisect reset