Adds git history squash <revision-range> to fold a range of commits into its
oldest one, reusing that commit's message and replaying any descendants on
top.

Changes in v3:

 * Moved the feature out of git rebase and into a new git history squash
   <revision-range> subcommand, per the list discussion. git rebase --squash
   is dropped.
 * Takes an arbitrary range (git history squash @~3.., git history squash
   @~5..@~2), folding it into the oldest commit and replaying any
   descendants on top.
 * Implemented as a single tree operation rather than picking each commit,
   so there are no repeated conflict stops (addresses Phillip's efficiency
   point).
 * A merge inside the range is folded fine, only a range with more than one
   base is rejected.
 * --reedit-message seeds the editor with every folded-in message, not just
   the oldest.

Harald Nordgren (4):
  history: extract helper for a commit's parent tree
  history: give commit_tree_ext a message template
  history: add squash subcommand to fold a range
  history: re-edit a squash with every message

 Documentation/git-history.adoc |  21 +++
 builtin/history.c              | 287 ++++++++++++++++++++++++++++-----
 t/meson.build                  |   1 +
 t/t3454-history-squash.sh      | 250 ++++++++++++++++++++++++++++
 4 files changed, 521 insertions(+), 38 deletions(-)
 create mode 100755 t/t3454-history-squash.sh

base-commit: 95e20213faefeb95df29277c58ac1980ab68f701

Submitted-As: https://lore.kernel.org/git/pull.2337.v3.git.git.1781810226.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.2337.git.git.1781465141.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.2337.v2.git.git.1781512625.gitgitgadget@gmail.com