Revert "update: checkout branch unconditionally"
Revert "update: checkout branch unconditionally"

This reverts commit 0525c9eeea27eff1a6de05e7a01ec268ae07437b.
Which breaks `brew update --rebase`.

joshfriend/homebrew,SuperNEMO-DBD/cadfaelbrew,kevinastone/homebrew,quantumsteve/homebrew,ralic/homebrew,sjackman/linuxbrew,yumitsu/homebrew,filcab/homebrew,ear/homebrew,ilovezfs/homebrew,josa42/homebrew,hanxue/homebrew,quantumsteve/homebrew,skinny-framework/homebrew,sometimesfood/homebrew,ExtremeMan/homebrew,muellermartin/homebrew,pcottle/homebrew,nandub/homebrew,AlexejK/homebrew,elgertam/homebrew,dongcarl/homebrew,optikfluffel/homebrew,muellermartin/homebrew,dutchcoders/homebrew,dickeyxxx/homebrew,Asuranceturix/homebrew,emcrisostomo/homebrew,filcab/homebrew,tutumcloud/homebrew,afh/homebrew,sometimesfood/homebrew,totalvoidness/homebrew,Homebrew/linuxbrew,dutchcoders/homebrew,sakra/homebrew,pcottle/homebrew,influxdb/homebrew,lrascao/homebrew,OJFord/homebrew,skinny-framework/homebrew,SuperNEMO-DBD/cadfaelbrew,elgertam/homebrew,theeternalsw0rd/homebrew,OJFord/homebrew,tschoonj/homebrew,gawbul/homebrew,skinny-framework/homebrew,ExtremeMan/homebrew,scorphus/homebrew,sakra/homebrew,dplarson/homebrew,reelsense/linuxbrew,liamstask/homebrew,cscetbon/homebrew,optikfluffel/homebrew,emcrisostomo/homebrew,reelsense/homebrew,Linuxbrew/linuxbrew,Angeldude/linuxbrew,ralic/homebrew,ExtremeMan/homebrew,influxdata/homebrew,filcab/homebrew,marcwebbie/homebrew,BrewTestBot/homebrew,tutumcloud/homebrew,pcottle/homebrew,marcwebbie/homebrew,hanxue/homebrew,scorphus/homebrew,booi/homebrew,Linuxbrew/linuxbrew,sferik/homebrew,AlexejK/homebrew,ablyler/homebrew,elgertam/homebrew,BrewTestBot/homebrew,pcottle/homebrew,pcottle/homebrew,Angeldude/linuxbrew,marcwebbie/homebrew,Linuxbrew/linuxbrew,lrascao/homebrew,Asuranceturix/homebrew,ear/homebrew,gnubila-france/linuxbrew,saketkc/linuxbrew,Homebrew/linuxbrew,gnubila-france/linuxbrew,georgschoelly/homebrew,totalvoidness/homebrew,dericed/homebrew,Homebrew/homebrew,chadcatlett/homebrew,SuperNEMO-DBD/cadfaelbrew,cscetbon/homebrew,ilovezfs/homebrew,sjackman/linuxbrew,deorth/homebrew,dongcarl/homebrew,gnubila-france/linuxbrew,afh/homebrew,SteveClement/homebrew,reelsense/homebrew,dplarson/homebrew,liamstask/homebrew,BrewTestBot/homebrew,afh/homebrew,getgauge/homebrew,influxdb/homebrew,SteveClement/homebrew,base10/homebrew,nandub/homebrew,josa42/homebrew,BrewTestBot/homebrew,getgauge/homebrew,dutchcoders/homebrew,dongcarl/homebrew,muellermartin/homebrew,ExtremeMan/homebrew,brunchboy/homebrew,reelsense/homebrew,base10/homebrew,dericed/homebrew,Homebrew/homebrew,Linuxbrew/linuxbrew,Homebrew/homebrew,influxdb/homebrew,influxdata/homebrew,mkrapp/homebrew,Asuranceturix/homebrew,marcwebbie/homebrew,reelsense/linuxbrew,liamstask/homebrew,muellermartin/homebrew,yumitsu/homebrew,chadcatlett/homebrew,filcab/homebrew,frodeaa/homebrew,base10/homebrew,sometimesfood/homebrew,afh/homebrew,brunchboy/homebrew,AlexejK/homebrew,ralic/homebrew,michaKFromParis/homebrew-sparks,frodeaa/homebrew,kevinastone/homebrew,optikfluffel/homebrew,Asuranceturix/homebrew,joshfriend/homebrew,sjackman/linuxbrew,tschoonj/homebrew,mkrapp/homebrew,3van/homebrew,scorphus/homebrew,tutumcloud/homebrew,dickeyxxx/homebrew,SteveClement/homebrew,3van/homebrew,Homebrew/linuxbrew,dickeyxxx/homebrew,michaKFromParis/homebrew-sparks,AlexejK/homebrew,cscetbon/homebrew,3van/homebrew,reelsense/linuxbrew,tutumcloud/homebrew,lrascao/homebrew,sferik/homebrew,ear/homebrew,yumitsu/homebrew,sferik/homebrew,kevinastone/homebrew,quantumsteve/homebrew,dutchcoders/homebrew,dericed/homebrew,benjaminfrank/homebrew,booi/homebrew,saketkc/linuxbrew,dplarson/homebrew,influxdata/homebrew,hanxue/homebrew,Angeldude/linuxbrew,ablyler/homebrew,quantumsteve/homebrew,deorth/homebrew,Homebrew/homebrew,frodeaa/homebrew,sometimesfood/homebrew,theeternalsw0rd/homebrew,influxdata/homebrew,booi/homebrew,theeternalsw0rd/homebrew,base10/homebrew,dericed/homebrew,sakra/homebrew,deorth/homebrew,georgschoelly/homebrew,SuperNEMO-DBD/cadfaelbrew,michaKFromParis/homebrew-sparks,emcrisostomo/homebrew,benjaminfrank/homebrew,SteveClement/homebrew,tschoonj/homebrew,hanxue/homebrew,optikfluffel/homebrew,benjaminfrank/homebrew,josa42/homebrew,brunchboy/homebrew,tschoonj/homebrew,ablyler/homebrew,nandub/homebrew,OJFord/homebrew,saketkc/linuxbrew,skinny-framework/homebrew,saketkc/linuxbrew,SteveClement/homebrew,gnubila-france/linuxbrew,elgertam/homebrew,gawbul/homebrew,3van/homebrew,totalvoidness/homebrew,frodeaa/homebrew,getgauge/homebrew,scorphus/homebrew,ralic/homebrew,ilovezfs/homebrew,Homebrew/linuxbrew,reelsense/linuxbrew,chadcatlett/homebrew,georgschoelly/homebrew,kevinastone/homebrew,joshfriend/homebrew,influxdb/homebrew,sferik/homebrew,Angeldude/linuxbrew,sjackman/linuxbrew,totalvoidness/homebrew,dplarson/homebrew,liamstask/homebrew,ear/homebrew,ilovezfs/homebrew,benjaminfrank/homebrew,georgschoelly/homebrew,sakra/homebrew,ablyler/homebrew,emcrisostomo/homebrew,theeternalsw0rd/homebrew,gawbul/homebrew,nandub/homebrew,brunchboy/homebrew,reelsense/homebrew,getgauge/homebrew,OJFord/homebrew,mkrapp/homebrew,dongcarl/homebrew,dickeyxxx/homebrew,Asuranceturix/homebrew