[PATCH v9 0/3] rebase: document, clean up, and introduce a config option for --rebase-merges

This patch series introduces a rebase.rebaseMerges config option to accommodate users who would like --rebase-merges to be on by default and to facilitate turning on --rebase-merges by default without configuration in a future version of Git. It also cleans up and documents the behavior of the --rebase-merges command line option to avoid confusion about how the config option and the command line option interact.

Changes from v8:
- Add braces around one-line else clause
- Remove unnecessary change to error message priority

Thanks to Phillip, Junio, Johannes and Sergey for your feedback on v8.

Alex Henrie (3):
  rebase: add documentation and test for --no-rebase-merges
  rebase: deprecate --rebase-merges=""
  rebase: add a config option for --rebase-merges

 Documentation/config/rebase.txt        | 10 ++++
 Documentation/git-rebase.txt           | 19 ++++---
 builtin/rebase.c                       | 70 ++++++++++++++++++++------
 t/t3422-rebase-incompatible-options.sh | 17 +++++++
 t/t3430-rebase-merges.sh               | 44 ++++++++++++++++
 5 files changed, 138 insertions(+), 22 deletions(-)

Range-diff against v8:
1:  09fb7c1b74 = 1:  a22b9d0da2 rebase: add documentation and test for --no-rebase-merges
2:  a846716a4a = 2:  112fee4833 rebase: deprecate --rebase-merges=""
3:  b12a3610ba ! 3:  868899cd6d rebase: add a config option for --rebase-merges
    @@ builtin/rebase.c: static int rebase_config(const char *var, const char *value, v
     +		if (opts->config_rebase_merges < 0) {
     +			opts->config_rebase_merges = 1;
     +			parse_rebase_merges_value(opts, value);
    -+		} else
    ++		} else {
     +			opts->rebase_cousins = 0;
    ++		}
     +		return 0;
     +	}
     +
    @@ builtin/rebase.c: int cmd_rebase(int argc, const char **argv, const char *prefix
      		if (ignore_whitespace)
      			strvec_push(&options.git_am_opts,
     @@ builtin/rebase.c: int cmd_rebase(int argc, const char **argv, const char *prefix)
    - 				break;
    - 
    - 		if (i >= 0 || options.type == REBASE_APPLY) {
    --			if (is_merge(&options))
    --				die(_("apply options and merge options "
    --					  "cannot be used together"));
    --			else if (options.autosquash == -1 && options.config_autosquash == 1)
    -+			if (options.autosquash == -1 && options.config_autosquash == 1)
    + 					  "cannot be used together"));
    + 			else if (options.autosquash == -1 && options.config_autosquash == 1)
      				die(_("apply options are incompatible with rebase.autoSquash.  Consider adding --no-autosquash"));
     +			else if (options.rebase_merges == -1 && options.config_rebase_merges == 1)
     +				die(_("apply options are incompatible with rebase.rebaseMerges.  Consider adding --no-rebase-merges"));
      			else if (options.update_refs == -1 && options.config_update_refs == 1)
      				die(_("apply options are incompatible with rebase.updateRefs.  Consider adding --no-update-refs"));
    -+			else if (is_merge(&options))
    -+				die(_("apply options and merge options "
    -+					  "cannot be used together"));
      			else
    - 				options.type = REBASE_APPLY;
    - 		}
     @@ builtin/rebase.c: int cmd_rebase(int argc, const char **argv, const char *prefix)
      	options.update_refs = (options.update_refs >= 0) ? options.update_refs :
      			     ((options.config_update_refs >= 0) ? options.config_update_refs : 0);