Git Tutorial 6: What is HEAD? Video Lecture | Git Tutorial: What is git / What is version control system? - Software Development

dear friends in this tutorial we are
going to learn what is head in gate head
is a reference to the most recent commit
in the current branch in most of the
cases the reason I said most of the
cases is because there are some cases
where this is not the case and we will
cover them later on I have this gate
repository where I have a bunch of
commits which I can list using git log
ok so I have these three commits now
head is nothing but a reference to this
commit I can verify by running this
command called git show head this will
show me the head commit this is same as
doing good show
this particular commit
okay so they produce the same output so
I can say head is just a short form of
writing this committee okay now let me
make one more commit and see what
happens to get so I'm going to add one
more line here and I will commit that
change so I read this and I will now
commit this it can make minus M murder
okay when I do that and if I run git log
I see this commit and when I do get show
head it will now show me barber commit
so as you can see in the diagram the
head pointer keeps on moving and it
always not always but in majority of the
cases it refers to the most recent
commit okay now let me show you another
another case where her head could be
useful and that is to do the death now
we have been running this get diff to
command in our previous tutorial so this
command is useful to show the difference
between two comments okay
so I'm going to run give give lift to
Khan to commit so for example from this
commit to this commit this Pisa line was
added okay and I want to see the
difference between the snapshot of this
and this so the way you do it is by
running git diff to the older commit
which is this so I'm just going to copy
paste that commit and the newer commit
which is this so again I'll be copying
and pasting when I do that or the MELD
diff tool will open and it will show me
the difference from left and right you
see this Pisa line was added between
those two commits so this is my old code
this is my new code okay now the same
thing you can do by using a head so I
can say head
now remember a head is here
so this commit will be head tilde 1 and
this comment will be head tilde - so you
always put the older commits first so I
will do head tilde - and he'll tilde 1
you can just say like head - - you know
this is 1 and this is this is head this
is head - 1 head - 2 so head - - and
head - 1 ok and when you do that you
will get the same output you'll see that
in this particular commit Pisa line was
added ok so this command is just a short
form of running this but the benefit
here is that you don't have to remember
the commit or copy/paste this long
commit ID you can just use this short
form so head at ta D it refers to this
head my head tilde 1 refers to this head
Taylor 2 refers to this particular
commit ie
ok now let's see how good internally
manages this head pointer if you have
your code repository open and if you
have if you are showing the hidden repos
hidden directories then there is always
a dot get directory in your current code
directory if this is not visible you can
go to Windows Explorer option and choose
the option to show hidden files ok but
once you have dot get directory open use
a bunch of files here and head is one of
the files now when I open this head file
I will say this so it is referring to a
master branch now if I have two branches
for example I
when I do get plans I have second branch
called thirsty now when I check out the
second branch my head pointer will
actually move to thirsty so see now it
updated this file and now I have thirsty
in my head ok now let me discuss the
scenario where head doesn't point to the
most recent commit that scenario is
called detached head so sometimes when
you do get log you want to go to this
previous comment ok and based on that
previous commit you want to make some
changes so you want to make this
particular commit your base and then
want to add further changes because you
want to ignore this in that case you
will do get check out this commit ok
let's see what happens when we run this
command ok it is showing me this message
that you are in detached head state
meaning head is not pointing to the most
recent commit it is add some older
commit ok and you can see that reflected
here as well usually it's a branch name
but now it is this particular thing ok
so now your head is in a detached state
and when I open my head file head is
having this commit ID for BC etc and
that was this commit ID for BC etc so
you can see how it manages all of these
things by using a simple text file ok
all right so now I want to come out of
the detached head state in that case you
can do get check out master and now you
are at master the PISA is the most
recent commit and when you do that you
will come out of the detached head state
all right okay so that was all about
head thank you for watching this video
we'll see you guys in the next tutorial