git/git-rebase.sh, branch v2.19.2

Merge branch 'en/rebase-consistency'

2018-07-24T21:50:43Z

"git rebase" behaved slightly differently depending on which one of the three backends gets used; this has been documented and an effort to make them more uniform has begun. * en/rebase-consistency: git-rebase: make --allow-empty-message the default t3401: add directory rename testcases for rebase and am git-rebase.txt: document behavioral differences between modes directory-rename-detection.txt: technical docs on abilities and limitations git-rebase.txt: address confusion between --no-ff vs --force-rebase git-rebase: error out when incompatible options passed t3422: new testcases for checking when incompatible options passed git-rebase.sh: update help messages a bit git-rebase.txt: document incompatible options

Merge branch 'en/rebase-i-microfixes'

2018-07-18T19:20:33Z

* en/rebase-i-microfixes: git-rebase--merge: modernize "git-$cmd" to "git $cmd" Fix use of strategy options with interactive rebases t3418: add testcase showing problems with rebase -i and strategy options

Fix use of strategy options with interactive rebases

2018-06-27T19:25:12Z

git-rebase.sh wrote strategy options to .git/rebase/merge/strategy_opts in the following format: '--ours' '--renormalize' Note the double spaces. git-rebase--interactive uses sequencer.c to parse that file, and sequencer.c used split_cmdline() to get the individual strategy options. After splitting, sequencer.c prefixed each "option" with a double dash, so, concatenating all its options would result in: -- --ours -- --renormalize So, when it ended up calling try_merge_strategy(), that in turn would run git merge-$strategy -- --ours -- --renormalize $merge_base -- $head $remote instead of the expected/desired git merge-$strategy --ours --renormalize $merge_base -- $head $remote Remove the extra spaces so that when it goes through split_cmdline() we end up with the desired command line. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

git-rebase: make --allow-empty-message the default

2018-06-27T18:23:22Z

rebase backends currently behave differently with empty commit messages, largely as a side-effect of the different underlying commands on which they are based. am-based rebases apply commits with an empty commit message without stopping or requiring the user to specify an extra flag. (It is interesting to note that am-based rebases are the default rebase type, and no one has ever requested a --no-allow-empty-message flag to change this behavior.) merge-based and interactive-based rebases (which are ultimately based on git-commit), will currently halt on any such commits and require the user to manually specify what to do with the commit and continue. One possible rationale for the difference in behavior is that the purpose of an "am" based rebase is solely to transplant an existing history, while an "interactive" rebase is one whose purpose is to polish a series before making it publishable. Thus, stopping and asking for confirmation for a possible problem is more appropriate in the latter case. However, there are two problems with this rationale: 1) merge-based rebases are also non-interactive and there are multiple types of rebases that use the interactive machinery but are not explicitly interactive (e.g. when either --rebase-merges or --keep-empty are specified without --interactive). These rebases are also used solely to transplant an existing history, and thus also should default to --allow-empty-message. 2) this rationale only says that the user is more accepting of stopping in the case of an explicitly interactive rebase, not that stopping for this particular reason actually makes sense. Exploring whether it makes sense, requires backing up and analyzing the underlying commands... If git-commit did not error out on empty commits by default, accidental creation of commits with empty messages would be a very common occurrence (this check has caught me many times). Further, nearly all such empty commit messages would be considered an accidental error (as evidenced by a huge amount of documentation across version control systems and in various blog posts explaining how important commit messages are). A simple check for what would otherwise be a common error thus made a lot of sense, and git-commit gained an --allow-empty-message flag for special case overrides. This has made commits with empty messages very rare. There are two sources for commits with empty messages for rebase (and cherry-pick): (a) commits created in git where the user previously specified --allow-empty-message to git-commit, and (b) commits imported into git from other version control systems. In case (a), the user has already explicitly specified that there is something special about this commit that makes them not want to specify a commit message; forcing them to re-specify with every cherry-pick or rebase seems more likely to be infuriating than helpful. In case (b), the commit is highly unlikely to have been authored by the person who has imported the history and is doing the rebase or cherry-pick, and thus the user is unlikely to be the appropriate person to write a commit message for it. Stopping and expecting the user to modify the commit before proceeding thus seems counter-productive. Further, note that while empty commit messages was a common error case for git-commit to deal with, it is a rare case for rebase (or cherry-pick). The fact that it is rare raises the question of why it would be worth checking and stopping on this particular condition and not others. For example, why doesn't an interactive rebase automatically stop if the commit message's first line is 2000 columns long, or is missing a blank line after the first line, or has every line indented with five spaces, or any number of other myriad problems? Finally, note that if a user doing an interactive rebase does have the necessary knowledge to add a message for any such commit and wants to do so, it is rather simple for them to change the appropriate line from 'pick' to 'reword'. The fact that the subject is empty in the todo list that the user edits should even serve as a way to notify them. As far as I can tell, the fact that merge-based and interactive-based rebases stop on commits with empty commit messages is solely a by-product of having been based on git-commit. It went without notice for a long time precisely because such cases are rare. The rareness of this situation made it difficult to reason about, so when folks did eventually notice this behavior, they assumed it was there for a good reason and just added an --allow-empty-message flag. In my opinion, stopping on such messages not desirable in any of these cases, even the (explicitly) interactive case. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

git-rebase: error out when incompatible options passed

2018-06-27T18:23:22Z

git rebase has three different types: am, merge, and interactive, all of which are implemented in terms of separate scripts. am builds on git-am, merge builds on git-merge-recursive, and interactive builds on git-cherry-pick. We make use of features in those lower-level commands in the different rebase types, but those features don't exist in all of the lower level commands so we have a range of incompatibilities. Previously, we just accepted nearly any argument and silently ignored whichever ones weren't implemented for the type of rebase specified. Change this so the incompatibilities are documented, included in the testsuite, and tested for at runtime with an appropriate error message shown. Some exceptions I left out: * --merge and --interactive are technically incompatible since they are supposed to run different underlying scripts, but with a few small changes, --interactive can do everything that --merge can. In fact, I'll shortly be sending another patch to remove git-rebase--merge and reimplement it on top of git-rebase--interactive. * One could argue that --interactive and --quiet are incompatible since --interactive doesn't implement a --quiet mode (perhaps since cherry-pick itself does not implement one). However, the interactive mode is more quiet than the other modes in general with progress messages, so one could argue that it's already quiet. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

git-rebase.sh: update help messages a bit

2018-06-26T18:00:12Z

signoff is not specific to the am-backend. Also, re-order a few options to make like things (e.g. strategy and strategy-option) be near each other. Signed-off-by: Elijah Newren Signed-off-by: Junio C Hamano

rebase: use the new git-rebase--preserve-merges.sh

2018-06-01T00:34:48Z

Create a new type of rebase, "preserve-merges", used when rebase is called with -p. Before that, the type for preserve-merges was "interactive", and some places of this script compared $type to "interactive". Instead, the code now checks if $interactive_rebase is empty or not, as it is set to "explicit" when calling an interactive rebase (and, possibly, one of its submodes), and "implied" when calling one of its submodes (eg. preserve-merges) *without* interactive rebase. It also detects the presence of the directory "$merge_dir"/rewritten left by the preserve-merges script when calling rebase --continue, --skip, etc., and, if it exists, sets the rebase mode to preserve-merges. In this case, interactive_rebase is set to "explicit", as "implied" would break some tests. Signed-off-by: Alban Gruin

rebase -i: introduce --rebase-merges=[no-]rebase-cousins

2018-04-26T03:28:43Z

When running `git rebase --rebase-merges` non-interactively with an ancestor of HEAD as (or leaving the todo list unmodified), we would ideally recreate the exact same commits as before the rebase. However, if there are commits in the commit range .. that do not have as direct ancestor (i.e. if `git log ..` would show commits that are omitted by `git log --ancestry-path ..`), this is currently not the case: we would turn them into commits that have as direct ancestor. Let's illustrate that with a diagram: C / \ A - B - E - F \ / D Currently, after running `git rebase -i --rebase-merges B`, the new branch structure would be (pay particular attention to the commit `D`): --- C' -- / \ A - B ------ E' - F' \ / D' This is not really preserving the branch topology from before! The reason is that the commit `D` does not have `B` as ancestor, and therefore it gets rebased onto `B`. This is unintuitive behavior. Even worse, when recreating branch structure, most use cases would appear to want cousins *not* to be rebased onto the new base commit. For example, Git for Windows (the heaviest user of the Git garden shears, which served as the blueprint for --rebase-merges) frequently merges branches from `next` early, and these branches certainly do *not* want to be rebased. In the example above, the desired outcome would look like this: --- C' -- / \ A - B ------ E' - F' \ / -- D' -- Let's introduce the term "cousins" for such commits ("D" in the example), and let's not rebase them by default. For hypothetical use cases where cousins *do* need to be rebased, `git rebase --rebase=merges=rebase-cousins` needs to be used. Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

rebase: introduce the --rebase-merges option

2018-04-26T03:28:43Z

Once upon a time, this here developer thought: wouldn't it be nice if, say, Git for Windows' patches on top of core Git could be represented as a thicket of branches, and be rebased on top of core Git in order to maintain a cherry-pick'able set of patch series? The original attempt to answer this was: git rebase --preserve-merges. However, that experiment was never intended as an interactive option, and it only piggy-backed on git rebase --interactive because that command's implementation looked already very, very familiar: it was designed by the same person who designed --preserve-merges: yours truly. Some time later, some other developer (I am looking at you, Andreas! ;-)) decided that it would be a good idea to allow --preserve-merges to be combined with --interactive (with caveats!) and the Git maintainer (well, the interim Git maintainer during Junio's absence, that is) agreed, and that is when the glamor of the --preserve-merges design started to fall apart rather quickly and unglamorously. The reason? In --preserve-merges mode, the parents of a merge commit (or for that matter, of *any* commit) were not stated explicitly, but were *implied* by the commit name passed to the `pick` command. This made it impossible, for example, to reorder commits. Not to mention to move commits between branches or, deity forbid, to split topic branches into two. Alas, these shortcomings also prevented that mode (whose original purpose was to serve Git for Windows' needs, with the additional hope that it may be useful to others, too) from serving Git for Windows' needs. Five years later, when it became really untenable to have one unwieldy, big hodge-podge patch series of partly related, partly unrelated patches in Git for Windows that was rebased onto core Git's tags from time to time (earning the undeserved wrath of the developer of the ill-fated git-remote-hg series that first obsoleted Git for Windows' competing approach, only to be abandoned without maintainer later) was really untenable, the "Git garden shears" were born [*1*/*2*]: a script, piggy-backing on top of the interactive rebase, that would first determine the branch topology of the patches to be rebased, create a pseudo todo list for further editing, transform the result into a real todo list (making heavy use of the `exec` command to "implement" the missing todo list commands) and finally recreate the patch series on top of the new base commit. That was in 2013. And it took about three weeks to come up with the design and implement it as an out-of-tree script. Needless to say, the implementation needed quite a few years to stabilize, all the while the design itself proved itself sound. With this patch, the goodness of the Git garden shears comes to `git rebase -i` itself. Passing the `--rebase-merges` option will generate a todo list that can be understood readily, and where it is obvious how to reorder commits. New branches can be introduced by inserting `label` commands and calling `merge `. And once this mode will have become stable and universally accepted, we can deprecate the design mistake that was `--preserve-merges`. Link *1*: https://github.com/msysgit/msysgit/blob/master/share/msysGit/shears.sh Link *2*: https://github.com/git-for-windows/build-extra/blob/master/shears.sh Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

Merge branch 'pw/rebase-signoff'

2018-04-25T04:28:51Z

"git rebase" has learned to honor "--signoff" option when using backends other than "am" (but not "--preserve-merges"). * pw/rebase-signoff: rebase --keep-empty: always use interactive rebase rebase -p: error out if --signoff is given rebase: extend --signoff support