[PATCH] branch: error description when deleting a not fully merged branch

["Rubén Justo" <rjusto@gmail.com>]

The error message we show when the user tries to delete a not fully
merged branch describes the error and gives a hint to the user:

	error: the branch 'foo' is not fully merged.
	If you are sure you want to delete it, run 'git branch -D foo'.

Let's move the hint part so that it takes advantage of the advice
machinery:

	error: the branch 'foo' is not fully merged
	hint: If you are sure you want to delete it, run 'git branch -D foo'
	hint: Disable this message with "git config advice.forceDeleteBranch false"

Signed-off-by: Rubén Justo <rjusto@gmail.com>
---

This change is a pending NEEDSWORK from a recent series about adjusting
the error messages in branch.c

Unfortunately the full message now becomes a three line message.

Hopefully we can find a way in the near future to keep it at two.

 Documentation/config/advice.txt | 3 +++
 advice.c                        | 1 +
 advice.h                        | 3 ++-
 builtin/branch.c                | 9 ++++++---
 4 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/Documentation/config/advice.txt b/Documentation/config/advice.txt
index 4d7e5d8759..5814d659b9 100644
--- a/Documentation/config/advice.txt
+++ b/Documentation/config/advice.txt
@@ -142,4 +142,7 @@ advice.*::
 		Advice shown when a user tries to create a worktree from an
 		invalid reference, to instruct how to create a new unborn
 		branch instead.
+	forceDeleteBranch::
+		Advice shown when a user tries to delete a not fully merged
+		branch without the force option set.
 --
diff --git a/advice.c b/advice.c
index 50c79443ba..e91f5d7ab8 100644
--- a/advice.c
+++ b/advice.c
@@ -79,6 +79,7 @@ static struct {
 	[ADVICE_UPDATE_SPARSE_PATH]			= { "updateSparsePath", 1 },
 	[ADVICE_WAITING_FOR_EDITOR]			= { "waitingForEditor", 1 },
 	[ADVICE_WORKTREE_ADD_ORPHAN]			= { "worktreeAddOrphan", 1 },
+	[ADVICE_FORCE_DELETE_BRANCH]			= { "forceDeleteBranch", 1 },
 };
 
 static const char turn_off_instructions[] =
diff --git a/advice.h b/advice.h
index 2affbe1426..5bef900142 100644
--- a/advice.h
+++ b/advice.h
@@ -10,7 +10,7 @@ struct string_list;
  * Add the new config variable to Documentation/config/advice.txt.
  * Call advise_if_enabled to print your advice.
  */
- enum advice_type {
+enum advice_type {
 	ADVICE_ADD_EMBEDDED_REPO,
 	ADVICE_ADD_EMPTY_PATHSPEC,
 	ADVICE_ADD_IGNORED_FILE,
@@ -50,6 +50,7 @@ struct string_list;
 	ADVICE_WAITING_FOR_EDITOR,
 	ADVICE_SKIPPED_CHERRY_PICKS,
 	ADVICE_WORKTREE_ADD_ORPHAN,
+	ADVICE_FORCE_DELETE_BRANCH,
 };
 
 int git_default_advice_config(const char *var, const char *value);
diff --git a/builtin/branch.c b/builtin/branch.c
index 0a32d1b6c8..2240433bc8 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -24,6 +24,7 @@
 #include "ref-filter.h"
 #include "worktree.h"
 #include "help.h"
+#include "advice.h"
 #include "commit-reach.h"
 
 static const char * const builtin_branch_usage[] = {
@@ -190,9 +191,11 @@ static int check_branch_commit(const char *branchname, const char *refname,
 		return -1;
 	}
 	if (!force && !branch_merged(kinds, branchname, rev, head_rev)) {
-		error(_("the branch '%s' is not fully merged.\n"
-		      "If you are sure you want to delete it, "
-		      "run 'git branch -D %s'"), branchname, branchname);
+		error(_("the branch '%s' is not fully merged"),
+		      branchname);
+		advise_if_enabled(ADVICE_FORCE_DELETE_BRANCH,
+				  _("If you are sure you want to delete it, "
+				  "run 'git branch -D %s'"), branchname);
 		return -1;
 	}
 	return 0;
-- 
2.42.0