call git rebase with the number of commits to be squashed

git rebase --interactive HEAD~2

the list of commits will be displayed

pick b76d157 b
pick a931ac7 c

mark the commits to be squashed in this case squash c into b

• press insert to enter edit mode
• mark commits to squash replacing pick by s or squash
• leave the first commit as pick
• to save and exit press ESC then type :wq (write quit)

pick b76d157 b
s a931ac7 c

edit the commit message

• press insert to enter edit mode
• edit the commit message
• to save and exit press ESC then type :wq (write quit)

# after that just edit the commit message


# This is a combination of 2 commits.
# The first commit's message is:

b

# This is the 2nd commit message:

c