1) Identify the commit short hash

    # git log --pretty=oneline --abbrev-commit
    abcd1234 Update to Fix for issue B
    cdababcd Fix issue B
    deab3412 Fix issue A
    ....
Here even `git log --oneline` also can be used to get short hash.

2) If you want to squash (merge) last two commit

    # git rebase -i deab3412 

3) This opens up a `nano` editor for merging. And it looks like below

    ....
    pick cdababcd Fix issue B
    pick abcd1234 Update to Fix for issue B
    ....

4) Rename the word `pick` to `squash` which is present before `abcd1234`. After rename it should be like below.

    ....
    pick cdababcd Fix issue B
    squash abcd1234 Update to Fix for issue B
    ....

5) Now save and close the `nano` editor. Press `ctrl + o` and press `Enter` to save. And then press `ctrl + x` to exit the editor.

6) Then `nano` editor again opens for updating comments, if necessary update it.

7) Now its squashed successfully, you can verify it by checking logs.

    # git log --pretty=oneline --abbrev-commit
    1122abcd Fix issue B
    deab3412 Fix issue A
    ....

8) Now push to repo. Note to add `+` sign before the branch name. This means forced push.

    # git push origin +master

Note : This is based on using git on `ubuntu` shell. If you are using different os (`Windows` or `Mac`) then above commands are same except editor. You might get different editor.