Merge Initials Request with airSlate SignNow

Merge initials request

hey everybody it's dan and gets cool dude once again with another get tutorial video today we're gonna be talking about the option of merge methods in a gitlab merger quest so if you've ever scrolled through all the settings in your project you may have noticed that there is a section called merge requests where you can select one of three merge methods today I'm going to explain what all three of these methods are by showing you visually how they affect the commit tree but before we do that if you're new to get or get lab in general I highly suggest you go over here to my playlist and watch a couple videos first if you don't understand get branches or the commit tree or how a tree base works or get lab in general then you might get lost watching this video so let's get started today we're actually not going to use the terminal I know I can hear the disappointment through YouTube this is an example commit tree with a master branch and a topic branch called topic a each circle is a commit each line is a parental relationship this notation simply shows that there's a lot more history below this but we are going to ignore it for the time being often when working in a team there are multiple topic branches branching off the particular locations where the master branch was at a particular point in time so for example here topic be branched off of master when master was located here and the same for topic see topic a branched off when master was down here if you're familiar with get lab merge request you'll know that every merge request has a destination branch which I'm going to show in this light blue color and of course a source branch which I'm going to show in this pink color so for example topic B is the source branch in this example master is the destination branch and when a merge happens meaning the merge button itself is clicked on the merge request page the content of topic B is merged into master master moves one commits ahead from where it was before and that's what happens in a typical merge when you click the merge button now what we just showed here in this tree is actually the default setting so this is selected by default you can see a merge commit as the default action it's created for every merge and merging is allowed as long as there's no merge conflicts of course just to be clear in the example of topic B here the merge was actually non fast-forward and it's worth noting that a merge commit will be made even if the merge could be fast forwarded so let me show you what that looks like consider this case or topic D here is fast forward ahead of master even though master could fast forward to the state of topic D with the default setting of the merge method a merge commit will be created anyway so that looks like this master was here it moves to here so here I'm just pointing out that with this methodology a merge commit is created for every single merge even if it's fast forward ahead making the tree look a little funky if you're not expecting this behavior it's worth pointing out here that these two commits actually have identical content meaning the files in the directory structure are identical if you were to check out from this commit to this commit or diff tool between them you're gonna get the exact same file state meaning no differences between these two states if that's not immediately clear to you think about it this way master before the merge was located at this commit topic D branched off changing the content in master by one commit this merge brings in no new content from master since topic D branched off of where master used to be which is why these two commits have the exact same content this is worth pointing out because this can have implications and get labs ci and we're gonna talk about that in a minute so if I back up slightly to before the merge a scenario where the source branch is fast forward ahead of the destination branch can actually be required before a merge request can be accepted that's actually the second option in these merge method options so you can see merge commit with semi linear history emerged commit is created for every merge but merging is only allowed if fast-forward merge is possible this way you could make sure that if this merge request would build after merging to the target branch it would also build and that's because of this relationship here where if gitlab CI is testing the tip of the source branch which is how it works then when the merge happens we know that by definition the content could not have changed so therefore the master branch after the merge is stable in the same testing that the topic D branch was stable in I hope that makes sense so both this setting and the third setting which we're going to talk about last have significant workflow implications that we're going to talk about next so with this semi linear history setting you can ensure your merge requests when merge will be stable with respect to your get lab CI testing but this actually forces all your developers to rebase their work on to the latest state of the destination branch because it requires a fast-forward merge this actually ends up creating a race condition where the first merge request to merge wins and subsequent M ARS must then rebase and retest over and over until their stuff gets in this can be a big deal or potentially not a big deal depending on your project but if your testing time takes several hours or let's say you have a whole bunch of developers that are all doing work all at the same time this type of workflow could be untenable so if you choose the semi linear history setting your tree of commits is actually going to end up looking like this now I've pointed out here where master used to be and where master is right now in this example topic one had two commits topic two had one commit and topic three had three commits and each one of these merge requests was required to be fast forward ahead of the branch they merged with at the time of the merge just like we pointed out before this commit and this commit have identical content the same with this commit and this commit and this commit in this commit so the third and last option is the fast-forward merge option so this is similar to the merge commit with semi linear history except the history is truly linear and there is no merge commit at all when the merge is complete for the example destination branch of Master and source branch topic D if we had a fast-forward merge the tree would change like this so the tree doesn't change master just fast forwards to the location of topic D so with the linear history setting your commit tree ends up looking like this it's structured similar to the semi linear history except you'll notice that the parental relationship between the tip of the master branch and where the master branch used to be compared to the topic commits the lines here do not exist this is truly linear history meaning each commit only has one parent all the way back into the tree which gives you a versioning system similar to something like subversion where there's no complex branching and parental relationships within the tree itself now of course with this history and the semi linear history option I'm just showing that what the tree looks like for the commits reachable from master of course there could be long-standing topic branches that were not showing and this little notation shows that there's more going on here but the point is that with respect to the destination branch of the merge request and all the topic aka source branches that come in the history will end up looking like this for the linear history case and this for the semi linear history case so that's pretty much it you guys a short video today just wanted to point out the three merge methods and how it affects the commit tree history a default setting is just a typical merge commit there is no right answer on which one of these I should use it depends a lot on your project that developers your testing time what your deploy process is there's a whole bunch of different factors that go into determining what the best merge method is this default setting works for most people which is why it's the default this option has the one potential downside that the integration branch the master in this particular video example the master branch can actually break because the CI testing only tests the tip of the source branch which is possible to actually break the master branch these two settings make that impossible but create constraints on your developer workflow which require them to always be fast forward ahead of the destination branch in the merge request thanks for watching do me a favor hit that like and subscribe button I'm Dan to get school dude and I'll see y'all next time