Improve pkg_delete(1) behaviour when deleting several packages at once.

Instead of trying to delete packages in the same order as they were specified
in the command line, reorder deletion in such a way that if package A depends
on package B then package A will be deleted before B no matter in which order
they were specified in the command line.

Reviewed by:	jkh, will
Approved by:	jkh

usr.sbin/pkg_install/delete/perform.c

@@ -30,16 +30,51 @@ static const char rcsid[] =
 static int pkg_do(char *);
 static void sanity_check(char *);
 static void undepend(PackingList, char *);
+static int chkifdepends(char *pkgname1, char *pkgname2);
 static char LogDir[FILENAME_MAX];
 
 
 int
 pkg_perform(char **pkgs)
 {
-    int i, err_cnt = 0;
+    char *tmp;
+    int i, j;
+    int err_cnt = 0;
+    int loop_cnt;
 
-    for (i = 0; pkgs[i]; i++)
+    for (i = 0; pkgs[i]; i++) {
+	/*
+	 * Check to see if any other package in pkgs[i+1:] depends
+	 * on pkgs[i] and deffer removal of pkgs[i] if so.
+	 */
+	loop_cnt = 0;
+	for (j = i + 1; pkgs[j]; j++) {
+	    if (chkifdepends(pkgs[j], pkgs[i]) == 1) {
+		/*
+		 * Try to avoid deadlock if package A depends on B which in
+		 * turn depends on C and C due to an error depends on A.
+		 * Use ugly but simple method, becase it Should Never
+		 * Happen[tm] in the real life anyway.
+		 */
+		if (loop_cnt > 4096) {
+		    warnx("dependency loop detected for package %s", pkgs[j]);
+		    err_cnt++;
+		    break;
+		}
+		loop_cnt++;
+		tmp = pkgs[i];
+		pkgs[i] = pkgs[j];
+		pkgs[j] = tmp;
+		/*
+		 * Another iteration requred to check if new pkgs[i]
+		 * itself has any packages that depend on it
+		 */
+		j--;
+	    }
+	}
 	err_cnt += pkg_do(pkgs[i]);
+    }
+
     return err_cnt;
 }
 
@@ -293,3 +328,39 @@ undepend(PackingList p, char *pkgname)
      remove(ftmp);			/* just in case */
      return;
 }
+
+/*
+ * Check to see if pkgname1 depends on pkgname2.
+ * Returns 1 if depends, 0 if not, and -1 if error occured.
+ */ 
+static int
+chkifdepends(char *pkgname1, char *pkgname2)
+{
+    FILE *fp;
+    char fname[FILENAME_MAX];
+    char fbuf[FILENAME_MAX];
+    char *tmp;
+    int retval;
+
+    sprintf(fname, "%s/%s/%s",
+	    (tmp = getenv(PKG_DBDIR)) ? tmp : DEF_LOG_DIR,
+	    pkgname2, REQUIRED_BY_FNAME);
+    fp = fopen(fname, "r");
+    if (fp == NULL) {
+	/* Probably pkgname2 doesn't have any packages that depend on it */
+	return 0;
+    }
+
+    retval = 0;
+    while (fgets(fbuf, sizeof(fbuf), fp) != NULL) {
+	if (fbuf[strlen(fbuf)-1] == '\n')
+	    fbuf[strlen(fbuf)-1] = '\0';
+	if (strcmp(fbuf, pkgname1) == 0) {	/* match */
+	    retval = 1;
+	    break;
+	}
+    }
+
+    fclose(fp);
+    return retval;
+}