rebase-merges: try and use branch names for labels

When interactively rebasing merge commits, the commit message is parsed to extract a probably meaningful label name. For instance if the merge commit is “Merge branch 'feature0'”, then the rebase script will have thes lines:

label feature0
merge -C $sha feature0 # “Merge branch 'feature0'

This heuristic fails in the case of octopus merges or when the merge commit message is actually unrelated to the parent commits.

An example that combines both is:

*---. 967bfa4 (HEAD -> integration) Integration

|\ \ \
| | | * 2135be1 (feature2, feat2) Feature 2
| |_|/
|/| |
| | * c88b01a Feature 1
| |/
|/|
| * 75f3139 (feat0) Feature 0
|/

* 25c86d0 (main) Initial commit

which yields the labels Integration, Integration-2 and Integration-3.

Fix this by using a branch name for each merge commit's parent that is the tip of at least one branch, and falling back to a label derived from the merge commit message otherwise. In the example above, the labels become feat0, Integration and feature2.

Changes since v1:

* moved load_branch_decorations to re-use the decoration_loaded guard and avoid pointlessly appending "refs/heads/" to a static string_list, as pointed out by Junio C Hamano (thanks!)
* fixed a leak in load_branch_decorations found by making the filter string_lists non-static

Changes since v2:

* style changes (true/false -> 1/0 and // -> /* */)

Nicolas Guichard (3):
load_branch_decorations: fix memory leak with non-static filters
rebase-update-refs: extract load_branch_decorations
rebase-merges: try and use branch names as labels

 log-tree.c                    | 26 +++++++++++++++++++++++++
 log-tree.h                    |  1 +
 sequencer.c                   | 36 +++++++++++++++++------------------
 t/t3404-rebase-interactive.sh |  4 ++--
 t/t3430-rebase-merges.sh      | 12 ++++++------
 5 files changed, 53 insertions(+), 26 deletions(-)

base-commit: 777489f9e09c8d0dd6b12f9d90de6376330577a2
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1784%2Fnicolas-guichard%2Fuse-branch-names-for-rebase-merges-labels-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1784/nicolas-guichard/use-branch-names-for-rebase-merges-labels-v3
Pull-Request: https://github.com/git/git/pull/1784

Range-diff vs v2:

1: 6250a7f6d6c ! 1: e030ddd91f3 load_branch_decorations: fix memory leak with non-static filters

     @@ log-tree.c: void load_ref_decorations(struct decoration_filter *filter, int flag
       				normalize_glob_ref(item, NULL, item->string);
       			}
      +
     -+			// normalize_glob_ref duplicates the strings
     -+			filter->exclude_ref_pattern->strdup_strings = true;
     -+			filter->include_ref_pattern->strdup_strings = true;
     -+			filter->exclude_ref_config_pattern->strdup_strings = true;
     ++			/* normalize_glob_ref duplicates the strings */
     ++			filter->exclude_ref_pattern->strdup_strings = 1;
     ++			filter->include_ref_pattern->strdup_strings = 1;
     ++			filter->exclude_ref_config_pattern->strdup_strings = 1;
       		}
       		decoration_loaded = 1;
       		decoration_flags = flags;
 2:  167418d10d1 ! 2:  1dad6096eb7 rebase-update-refs: extract load_branch_decorations
     @@ log-tree.c: void load_ref_decorations(struct decoration_filter *filter, int flag
      +		string_list_append(&decorate_refs_include, "refs/heads/");
      +		load_ref_decorations(&decoration_filter, 0);
      +
     -+		string_list_clear(&decorate_refs_exclude, false);
     -+		string_list_clear(&decorate_refs_exclude_config, false);
     -+		string_list_clear(&decorate_refs_include, false);
     ++		string_list_clear(&decorate_refs_exclude, 0);
     ++		string_list_clear(&decorate_refs_exclude_config, 0);
     ++		string_list_clear(&decorate_refs_include, 0);
      +	}
      +}
      +

3: dfa1f0a7648 = 3: 19d8253da07 rebase-merges: try and use branch names as labels

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