How to remove file and commit from history in git (how to remove the commit history in GIT)

Assume that our commit tree is as follows:

R-A-B-C-D-E-HEAD

Preparations:

Rm-RF. Git test.txt

Touch test.txt & git init & git add.
Echo "R"> test.txt & git ci-a-m "R"
Echo "A"> test.txt & git ci-a-m ""
Echo "B"> test.txt & git ci-a-m "B"
Echo "C"> test.txt & git ci-a-m "C"
Echo "D"> test.txt & git ci-a-m "D"
Echo "E"> test.txt & git ci-a-m "e"

Next, we will remove the commit tree of B and C and change it

R-A D-E-HEAD

There are two ways to remove B & C:

Method 1:

# Detach head and move to d commit
Git checkkout <SHA1-for-D>

# Move head to a, but leave the index and working tree as for d
Git reset -- soft <SHA1-for-A>

# Redo the D commit re-using the commit message, but now on top of
Git commit-C <SHA1-for-D>

Here, you can add, delete (some temporary files accidentally submitted), and then submit.

# Re-apply everything from the old d onwards onto this new place
Git rebase -- onto head <SHA1-for-D> master

# Push it
Git push -- force

Method 2: Use cherry-pick

Git rereset -- hard <sha1 of a>
Git cherry-pick <sha1 of D>
Git cherry-pick <sha1 of E>

Possible problems

Http://rwmj.wordpress.com/2010/05/14/git-cherry-pick-wins/

If it's unable to apply the patch directly, then you'll see a message

Like this:

Automatic cherry-pick failed. After resolving the conflicts,
Mark the corrected paths with 'git add <paths> 'or 'git Rm <paths>' and commit the result.
When commiting, use the option '-C 94e310d' to retain authorship and message.

This is fairly self-explanatory. Use "Git status" to see which files
Are problematic:

Edit the file to manually resolve the conflict, add the file, and then
Commit with the "-C" option noted in the original message.

The bad thing about cherry-pick is that if D is followed by multiple commits, the command should be executed multiple times, and conflicts may need to be resolved manually.

Both methods directly ignore the history of B and C, but the changes made by B and C still exist.
Commit history is removed.

For more information, see git help cherry-pick or git help rebase.

Refer:
Git: removing selected commits from Repository
Http://stackoverflow.com/questions/495345/git-removing-selected-commits-from-repository
Git: how to remove file and commit from history
Http://bogdan.org.ua/2009/02/13/git-how-to-remove-file-commit-from-history.html
Re :! [Rejected] Master-> master (non-fast forward)
Http://kerneltrap.org/mailarchive/git/2007/11/18/425729