advice: add diverging advice for novices

The user might not necessarily know why ff only was configured, maybe an
admin did it, or the installer (Git for Windows), or perhaps they just
followed some online advice.

This can happen not only on pull.ff=only, but merge.ff=only too.

Even worse if the user has configured pull.rebase=false and
merge.ff=only, because in those cases a diverging merge will constantly
keep failing. There's no trivial way to get out of this other than
`git merge --no-ff`.

Let's not assume our users are experts in git who completely understand
all their configurations.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Acked-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/config/advice.txt b/Documentation/config/advice.txt
index a00d010..c96b5b2 100644 (file)
--- a/Documentation/config/advice.txt
+++ b/Documentation/config/advice.txt
@@ -136,4 +136,6 @@ advice.*::
                Advice shown when either linkgit:git-add[1] or linkgit:git-rm[1]
                is asked to update index entries outside the current sparse
                checkout.
+       diverging::
+               Advice shown when a fast-forward is not possible.
 --

diff --git a/advice.c b/advice.c
index fd18968..fbc59f9 100644 (file)
--- a/advice.c
+++ b/advice.c
@@ -44,6 +44,7 @@ static struct {
        [ADVICE_COMMIT_BEFORE_MERGE]                    = { "commitBeforeMerge", 1 },
        [ADVICE_DETACHED_HEAD]                          = { "detachedHead", 1 },
        [ADVICE_SUGGEST_DETACHING_HEAD]                 = { "suggestDetachingHead", 1 },
+       [ADVICE_DIVERGING]                              = { "diverging", 1 },
        [ADVICE_FETCH_SHOW_FORCED_UPDATES]              = { "fetchShowForcedUpdates", 1 },
        [ADVICE_GRAFT_FILE_DEPRECATED]                  = { "graftFileDeprecated", 1 },
        [ADVICE_IGNORED_HOOK]                           = { "ignoredHook", 1 },
@@ -217,6 +218,14 @@ void NORETURN die_conclude_merge(void)
 
 void NORETURN die_ff_impossible(void)
 {
+       advise_if_enabled(ADVICE_DIVERGING,
+               _("Diverging branches can't be fast-forwarded, you need to either:\n"
+               "\n"
+               "\tgit merge --no-ff\n"
+               "\n"
+               "or:\n"
+               "\n"
+               "\tgit rebase\n"));
        die(_("Not possible to fast-forward, aborting."));
 }
 

diff --git a/advice.h b/advice.h
index 07e0f76..41b5bc1 100644 (file)
--- a/advice.h
+++ b/advice.h
@@ -21,6 +21,7 @@ struct string_list;
        ADVICE_CHECKOUT_AMBIGUOUS_REMOTE_BRANCH_NAME,
        ADVICE_COMMIT_BEFORE_MERGE,
        ADVICE_DETACHED_HEAD,
+       ADVICE_DIVERGING,
        ADVICE_SUGGEST_DETACHING_HEAD,
        ADVICE_FETCH_SHOW_FORCED_UPDATES,
        ADVICE_GRAFT_FILE_DEPRECATED,