[PATCH v4 0/4] Enhance git-rebases flexibiilty in handling empty commits

git's ability to handle empty commits is somewhat lacking, especially when preforming a rebase. Nominally empty commits are undesireable entries, the result of commits that are made empty by prior commits covering the same changs. But occasionally, empty commits are useful to developers (e.g. inserting notes into the development history without changing any code along the way). In these cases its desireable to easily preserve empty commits during operations like rebases.

This patch series enhances git to do just that. It adds two options to the git-cherry-pick command, --allow-empty, which allows git cherry-pick to preserve an empty commit, even if the fast forward logic isn't applicable during the operation, and --keep-redundant-commits, which allows the user to also keep commits that were made empty via conflict resolution. It also enhances git-rebase to add a --keep-empty option which enables rebases to preserve empty commits.

I've tested these operations out myself here and they work well for me

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>

--- Change notes:

Based on version 1 feedback from this list, the following changes have been made

V2)
	* Changed --keep-empty to --allow-empty in the git cherry-pick command

	* Converted run_git_commit to use argv_array

	* Updated cherry-pick --allow-empty description in man page
	
	* added ignore-if-made-empty option to git-cherry-pick

	* Added test to test suite to validate the new cherry-pick options

	* Updated git-rebase man page to be less verbose and more accurate in the
	description of the keep-empty option

	* squashed the addition of the keep-empty flag in git-rebase down to one
	commit from 3

	* fixed up coding style in git-rebase script

	* Optimized detection of empty commits

	* Only augmented git-rebase-editor message if empty commits are
	possible
	
V3)
	* reversed the --ignore-if-empty-logic to by default only keep initially
	empty commits

	* replaced --ignore-if-empty with --keep-redundant-commits, to allow
	empty commits that are made empty via conflict resolution, in addition
	to commits that were created as empty

	* reworked is_original_commit_empty to be more efficient and portable

	* Misc sylistic and spelling cleanups

V4)
	* Reverted the cherry-pick advice changes in V3 based on in-thread
	discussion

	* Rewrote my changes to is_original_commit_empty and run_git_commit to
	not have to fork, making them more efficient.