Various commands refuse to run in the presence of conflicts (commit,
merge, pull, cherry-pick/revert). They all used to provide rough, and
inconsistant error messages.
A new variable advice.resolveconflict is introduced, and allows more
verbose messages, pointing the user to the appropriate solution.
For commit, the error message used to look like this:
$ git commit
foo.txt: needs merge
foo.txt: unmerged (
c34a92682e0394bc0d6f4d4a67a8e2d32395c169)
foo.txt: unmerged (
3afcd75de8de0bb5076942fcb17446be50451030)
foo.txt: unmerged (
c9785d77b76dfe4fb038bf927ee518f6ae45ede4)
error: Error building trees
The "need merge" line is given by refresh_cache. We add the IN_PORCELAIN
option to make the output more consistant with the other porcelain
commands, and catch the error in return, to stop with a clean error
message. The next lines were displayed by a call to cache_tree_update(),
which is not reached anymore if we noticed the conflict.
The new output looks like:
U       foo.txt
fatal: 'commit' is not possible because you have unmerged files.
Please, fix them up in the work tree, and then use 'git add/rm <file>' as
appropriate to mark resolution and make a commit, or use 'git commit -a'.
Pull is slightly modified to abort immediately if $GIT_DIR/MERGE_HEAD
exists instead of waiting for merge to complain.
The behavior of merge and the test-case are slightly modified to reflect
the usual flow: start with conflicts, fix them, and afterwards get rid of
MERGE_HEAD, with different error messages at each stage.
Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
 
                Advice shown when linkgit:git-merge[1] refuses to
                merge to avoid overwritting local changes.
                Default: true.
+       resolveConflict::
+               Advices shown by various commands when conflicts
+               prevent the operation from being performed.
+               Default: true.
 --
 
 core.fileMode::
 
 int advice_push_nonfastforward = 1;
 int advice_status_hints = 1;
 int advice_commit_before_merge = 1;
+int advice_resolve_conflict = 1;
 
 static struct {
        const char *name;
        { "pushnonfastforward", &advice_push_nonfastforward },
        { "statushints", &advice_status_hints },
        { "commitbeforemerge", &advice_commit_before_merge },
+       { "resolveconflict", &advice_resolve_conflict },
 };
 
 int git_default_advice_config(const char *var, const char *value)
 
        return 0;
 }
+
+void NORETURN die_resolve_conflict(const char *me)
+{
+       if (advice_resolve_conflict)
+               /*
+                * Message used both when 'git commit' fails and when
+                * other commands doing a merge do.
+                */
+               die("'%s' is not possible because you have unmerged files.\n"
+                   "Please, fix them up in the work tree, and then use 'git add/rm <file>' as\n"
+                   "appropriate to mark resolution and make a commit, or use 'git commit -a'.", me);
+       else
+               die("'%s' is not possible because you have unmerged files.", me);
+}
 
 #ifndef ADVICE_H
 #define ADVICE_H
 
+#include "git-compat-util.h"
+
 extern int advice_push_nonfastforward;
 extern int advice_status_hints;
 extern int advice_commit_before_merge;
+extern int advice_resolve_conflict;
 
 int git_default_advice_config(const char *var, const char *value);
 
+extern void NORETURN die_resolve_conflict(const char *me);
+
 #endif /* ADVICE_H */
 
                exit(128); /* We've already reported the error, finish dying */
 }
 
+static void refresh_cache_or_die(int refresh_flags)
+{
+       /*
+        * refresh_flags contains REFRESH_QUIET, so the only errors
+        * are for unmerged entries.
+        */
+       if (refresh_cache(refresh_flags | REFRESH_IN_PORCELAIN))
+               die_resolve_conflict("commit");
+}
+
 static char *prepare_index(int argc, const char **argv, const char *prefix, int is_status)
 {
        int fd;
        if (all || (also && pathspec && *pathspec)) {
                int fd = hold_locked_index(&index_lock, 1);
                add_files_to_cache(also ? prefix : NULL, pathspec, 0);
-               refresh_cache(refresh_flags);
+               refresh_cache_or_die(refresh_flags);
                if (write_cache(fd, active_cache, active_nr) ||
                    close_lock_file(&index_lock))
                        die("unable to write new_index file");
         */
        if (!pathspec || !*pathspec) {
                fd = hold_locked_index(&index_lock, 1);
-               refresh_cache(refresh_flags);
+               refresh_cache_or_die(refresh_flags);
                if (write_cache(fd, active_cache, active_nr) ||
                    commit_locked_index(&index_lock))
                        die("unable to write new_index file");
 
        const char *best_strategy = NULL, *wt_strategy = NULL;
        struct commit_list **remotes = &remoteheads;
 
-       if (file_exists(git_path("MERGE_HEAD")))
-               die("You have not concluded your merge. (MERGE_HEAD exists)");
-       if (read_cache_unmerged())
-               die("You are in the middle of a conflicted merge."
-                               " (index unmerged)");
+       if (read_cache_unmerged()) {
+               die_resolve_conflict("merge");
+       }
+       if (file_exists(git_path("MERGE_HEAD"))) {
+               /*
+                * There is no unmerged entry, don't advise 'git
+                * add/rm <file>', just 'git commit'.
+                */
+               if (advice_resolve_conflict)
+                       die("You have not concluded your merge (MERGE_HEAD exists).\n"
+                           "Please, commit your changes before you can merge.");
+               else
+                       die("You have not concluded your merge (MERGE_HEAD exists).");
+       }
 
        /*
         * Check if we are _not_ on a detached HEAD, i.e. if there is a
 
        return tree;
 }
 
+static NORETURN void die_dirty_index(const char *me)
+{
+       if (read_cache_unmerged()) {
+               die_resolve_conflict(me);
+       } else {
+               if (advice_commit_before_merge)
+                       die("Your local changes would be overwritten by %s.\n"
+                           "Please, commit your changes or stash them to proceed.", me);
+               else
+                       die("Your local changes would be overwritten by %s.\n", me);
+       }
+}
+
 static int revert_or_cherry_pick(int argc, const char **argv)
 {
        unsigned char head[20];
                if (get_sha1("HEAD", head))
                        die ("You do not have a valid HEAD");
                if (index_differs_from("HEAD", 0))
-                       die ("Dirty index: cannot %s", me);
+                       die_dirty_index(me);
        }
        discard_cache();
 
 
 require_work_tree
 cd_to_toplevel
 
-test -z "$(git ls-files -u)" ||
-       die "You are in the middle of a conflicted merge."
+
+die_conflict () {
+    git diff-index --cached --name-status -r --ignore-submodules HEAD --
+    if [ $(git config --bool --get advice.resolveConflict || echo true) = "true" ]; then
+       die "Pull is not possible because you have unmerged files.
+Please, fix them up in the work tree, and then use 'git add/rm <file>'
+as appropriate to mark resolution, or use 'git commit -a'."
+    else
+       die "Pull is not possible because you have unmerged files."
+    fi
+}
+
+die_merge () {
+    if [ $(git config --bool --get advice.resolveConflict || echo true) = "true" ]; then
+       die "You have not concluded your merge (MERGE_HEAD exists).
+Please, commit your changes before you can merge."
+    else
+       die "You have not concluded your merge (MERGE_HEAD exists)."
+    fi
+}
+
+test -z "$(git ls-files -u)" || die_conflict
+test -f "$GIT_DIR/MERGE_HEAD" && die_merge
 
 strategy_args= diffstat= no_commit= squash= no_ff= ff_only=
 log_arg= verbosity=
 
 
        test_must_fail git merge "$c5" &&
        test_must_fail git merge "$c5" 2> out &&
+       grep "not possible because you have unmerged files" out &&
+       git add -u &&
+       test_must_fail git merge "$c5" 2> out &&
        grep "You have not concluded your merge" out &&
        rm -f .git/MERGE_HEAD &&
        test_must_fail git merge "$c5" 2> out &&
-       grep "You are in the middle of a conflicted merge" out
-
+       grep "Your local changes to .* would be overwritten by merge." out
 '
 
 test_expect_success 'merge-recursive remove conflict' '
 
        echo content >extra_file &&
        git add extra_file &&
        test_must_fail git revert HEAD 2>errors &&
-       grep "Dirty index" errors
+       grep "Your local changes would be overwritten by " errors
 
 '