bisect: add "check_good_are_ancestors_of_bad" function

This is a port of the function with the same name that is in
"git-bisect.sh". The new function is not used yet but will be in
a later patch.

We also implement an helper "check_ancestors" function that use
"start_command" and "finish_command" to launch
"git rev-list $good ^$bad".

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/bisect.c b/bisect.c
index b24ee78ba993803d125cacd50a85fd6f8b7327e5..09102daba8ac508ea3457bb43fcac0f0fd83ebeb 100644 (file)
--- a/bisect.c
+++ b/bisect.c
@@ -750,6 +750,81 @@ static void check_merge_bases(void)
        free_commit_list(result);
 }
 
+/*
+ * This function runs the command "git rev-list $_good ^$_bad"
+ * and returns 1 if it produces some output, 0 otherwise.
+ */
+static int check_ancestors(void)
+{
+       struct argv_array rev_argv = { NULL, 0, 0 };
+       struct strbuf str = STRBUF_INIT;
+       int i, result = 0;
+       struct child_process rls;
+       FILE *rls_fout;
+
+       argv_array_push(&rev_argv, xstrdup("rev-list"));
+       argv_array_push_sha1(&rev_argv, current_bad_sha1, "^%s");
+       for (i = 0; i < good_revs.sha1_nr; i++)
+               argv_array_push_sha1(&rev_argv, good_revs.sha1[i], "%s");
+       argv_array_push(&rev_argv, NULL);
+
+       memset(&rls, 0, sizeof(rls));
+       rls.argv = rev_argv.argv;
+       rls.out = -1;
+       rls.git_cmd = 1;
+       if (start_command(&rls))
+               die("Could not launch 'git rev-list' command.");
+       rls_fout = fdopen(rls.out, "r");
+       while (strbuf_getline(&str, rls_fout, '\n') != EOF) {
+               strbuf_trim(&str);
+               if (*str.buf) {
+                       result = 1;
+                       break;
+               }
+       }
+       fclose(rls_fout);
+       finish_command(&rls);
+
+       return result;
+}
+
+/*
+ * "check_good_are_ancestors_of_bad" checks that all "good" revs are
+ * ancestor of the "bad" rev.
+ *
+ * If that's not the case, we need to check the merge bases.
+ * If a merge base must be tested by the user, its source code will be
+ * checked out to be tested by the user and we will exit.
+ */
+static void check_good_are_ancestors_of_bad(const char *prefix)
+{
+       const char *filename = git_path("BISECT_ANCESTORS_OK");
+       struct stat st;
+       int fd;
+
+       if (!current_bad_sha1)
+               die("a bad revision is needed");
+
+       /* Check if file BISECT_ANCESTORS_OK exists. */
+       if (!stat(filename, &st) && S_ISREG(st.st_mode))
+               return;
+
+       /* Bisecting with no good rev is ok. */
+       if (good_revs.sha1_nr == 0)
+               return;
+
+       if (check_ancestors())
+               check_merge_bases();
+
+       /* Create file BISECT_ANCESTORS_OK. */
+       fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
+       if (fd < 0)
+               warning("could not create file '%s': %s",
+                       filename, strerror(errno));
+       else
+               close(fd);
+}
+
 /*
  * We use the convention that exiting with an exit code 10 means that
  * the bisection process finished successfully.