04_06_undoing.txt

#========================================================================
#    EPISODE - UNDOING CHANGES
#    SECTION - UNDO CHANGES ASSOCIATED WITH A COMMIT (RESET)
#========================================================================

# RESTORE A PREVIOUS STATE BY DELETING HISTORY (`git reset --hard`)
 
# git reset has several uses, and is most often used to unstage files 
# from the staging area i.e. git reset or git reset <file>.
# We are going to use a variant git reset --hard <commit> to reset things 
# to how they were at <commit>. 
# 
# This is a permanent undo which deletes all changes more recent than 
# <commit> from your history. 
#
# There is clearly potential here to lose work, so use this command with 
# care.Let’s try that on our paper, using the same example as before. 
#
# Now we have two commits which we want to abandon: 
# - the commit outlining the unreliable instrumentation
# - the subsequent revert commit
#
# We can achieve this by resetting to the last commit we want to keep.
# We can do that by running:
# 

git reset --hard HEAD~2	

# This moves tip of branch to two commits before HEAD
# HEAD is now at the commit 
# "Add methodology section and update references file"

# This moves the tip of the branch back to the specified commit. 
# If we look in-depth, this command moves back two pointers: 
# HEAD and the pointer to the tip of the branch we currently are working 
# on (master). 
# (HEAD~ = the commit right before HEAD; HEAD~2 = two commits before HEAD)
# The final effect is what we need: we abandoned the commits and we are now 
# back to where we were before making the commit about the data we are not using.