delta: Support filtering what type of deltas to show

Not everyone is interested in every kind of deltas (and some might
even be interested knowing which files do not have overrides), so this
here is an implementation of a --type=LIST... option for
systemd-delta, that makes it possible to filter what subset of deltas
we want.

The available modifiers are masked, equivalent, redirected, overriden,
and unchanged - they should be self explanatory, and the man page
explains them in a little more detail anyway.

As a side effect, in case of overriden files, the diff output was made
optional.

By default, everything is shown (with a diff, if appropriate) except
for completely unchanged files.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>

2 files changed, 183 insertions, 16 deletions

diff --git a/man/systemd-delta.xml b/man/systemd-delta.xml
index 0e06b48fcc..03c7178d47 100644
--- a/man/systemd-delta.xml
+++ b/man/systemd-delta.xml
@@ -99,6 +99,66 @@
 				pager.</para></listitem>
 			</varlistentry>
 
+                        <varlistentry>
+                                <term><option>--type=</option></term>
+                                <term><option>-t</option></term>
+
+                                <listitem><para>When listing the
+                                differences, only list those that are
+                                asked for. The list itself is a
+                                comma-separated list of desired
+                                difference types.</para>
+
+                                <para>Recognised types are:
+
+                                        <variablelist>
+                                                <varlistentry>
+                                                        <term><varname>masked</varname></term>
+
+                                                        <listitem><para>Show masked files</para></listitem>
+                                                </varlistentry>
+
+                                                <varlistentry>
+                                                        <term><varname>equivalent</varname></term>
+
+                                                        <listitem><para>Show overriden
+                                                        files that while overriden, do
+                                                        not differ in content.</para></listitem>
+                                                </varlistentry>
+
+                                                <varlistentry>
+                                                        <term><varname>redirected</varname></term>
+
+                                                        <listitem><para>Show files that
+                                                        are redirected to another.</para></listitem>
+                                                </varlistentry>
+
+                                                <varlistentry>
+                                                        <term><varname>overriden</varname></term>
+
+                                                        <listitem><para>Show overriden,
+                                                        and changed files.</para></listitem>
+                                                </varlistentry>
+
+                                                <varlistentry>
+                                                        <term><varname>unchanged</varname></term>
+
+                                                        <listitem><para>Show unmodified
+                                                        files too.</para></listitem>
+                                                </varlistentry>
+                                        </variablelist>
+                                </para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
+                                <term><option>--diff=</option></term>
+
+                                <listitem><para>When showing modified
+                                files, when a file is overriden show a
+                                diff aswell. This option takes a
+                                boolean argument.</para></listitem>
+                        </varlistentry>
+
                 </variablelist>
 
         </refsect1>
diff --git a/src/delta/delta.c b/src/delta/delta.c
index 2e3375941d..585bb0c7a7 100644
--- a/src/delta/delta.c
+++ b/src/delta/delta.c
@@ -55,7 +55,57 @@ static int equivalent(const char *a, const char *b) {
         return r;
 }
 
-static int found_override(const char *top, const char *bottom) {
+#define SHOW_MASKED		1 << 0
+#define SHOW_EQUIV		1 << 1
+#define SHOW_REDIR		1 << 2
+#define SHOW_OVERRIDEN		1 << 3
+#define SHOW_UNCHANGED		1 << 4
+#define SHOW_DIFF		1 << 5
+
+#define SHOW_DEFAULTS \
+        (SHOW_MASKED | SHOW_EQUIV | SHOW_REDIR | SHOW_OVERRIDEN | SHOW_DIFF)
+
+static int notify_override_masked(int flags, const char *top, const char *bottom) {
+        if (!(flags & SHOW_MASKED))
+                return 0;
+
+        printf(ANSI_HIGHLIGHT_RED_ON "[MASK]" ANSI_HIGHLIGHT_OFF "       %s → %s\n", top, bottom);
+        return 1;
+}
+
+static int notify_override_equiv(int flags, const char *top, const char *bottom) {
+        if (!(flags & SHOW_EQUIV))
+                return 0;
+
+        printf(ANSI_HIGHLIGHT_GREEN_ON "[EQUIVALENT]" ANSI_HIGHLIGHT_OFF " %s → %s\n", top, bottom);
+        return 1;
+}
+
+static int notify_override_redir(int flags, const char *top, const char *bottom) {
+        if (!(flags & SHOW_REDIR))
+                return 0;
+
+        printf(ANSI_HIGHLIGHT_ON "[REDIRECT]" ANSI_HIGHLIGHT_OFF "   %s → %s\n", top, bottom);
+        return 1;
+}
+
+static int notify_override_overriden(int flags, const char *top, const char *bottom) {
+        if (!(flags & SHOW_OVERRIDEN))
+                return 0;
+
+        printf(ANSI_HIGHLIGHT_ON "[OVERRIDE]" ANSI_HIGHLIGHT_OFF "   %s → %s\n", top, bottom);
+        return 1;
+}
+
+static int notify_override_unchanged(int flags, const char *top, const char *bottom) {
+        if (!(flags & SHOW_UNCHANGED))
+                return 0;
+
+        printf(ANSI_HIGHLIGHT_ON "[UNCHANGED]" ANSI_HIGHLIGHT_OFF "   %s → %s\n", top, bottom);
+        return 1;
+}
+
+static int found_override(int flags, const char *top, const char *bottom) {
         char *dest;
         int k;
         pid_t pid;
@@ -64,22 +114,24 @@ static int found_override(const char *top, const char *bottom) {
         assert(bottom);
 
         if (null_or_empty_path(top) > 0) {
-                printf(ANSI_HIGHLIGHT_RED_ON "[MASK]" ANSI_HIGHLIGHT_OFF "       %s → %s\n", top, bottom);
+                notify_override_masked(flags, top, bottom);
                 goto finish;
         }
 
         k = readlink_malloc(top, &dest);
         if (k >= 0) {
                 if (equivalent(dest, bottom) > 0)
-                        printf(ANSI_HIGHLIGHT_GREEN_ON "[EQUIVALENT]" ANSI_HIGHLIGHT_OFF " %s → %s\n", top, bottom);
+                        notify_override_equiv(flags, top, bottom);
                 else
-                        printf(ANSI_HIGHLIGHT_ON "[REDIRECT]" ANSI_HIGHLIGHT_OFF "   %s → %s\n", top, bottom);
+                        notify_override_redir(flags, top, bottom);
 
                 free(dest);
                 goto finish;
         }
 
-        printf(ANSI_HIGHLIGHT_ON "[OVERRIDE]" ANSI_HIGHLIGHT_OFF "   %s → %s\n", top, bottom);
+        notify_override_overriden(flags, top, bottom);
+        if (!(flags & SHOW_DIFF))
+                goto finish;
 
         putchar('\n');
 
@@ -174,7 +226,7 @@ finish:
         return r;
 }
 
-static int process_suffix(const char *prefixes, const char *suffix) {
+static int process_suffix(int flags, const char *prefixes, const char *suffix) {
         const char *p;
         char *f;
         Hashmap *top, *bottom;
@@ -220,10 +272,12 @@ static int process_suffix(const char *prefixes, const char *suffix) {
                 o = hashmap_get(bottom, path_get_file_name(f));
                 assert(o);
 
-                if (path_equal(o, f))
+                if (path_equal(o, f)) {
+                        notify_override_unchanged(flags, f, o);
                         continue;
+                }
 
-                k = found_override(f, o);
+                k = found_override(flags, f, o);
                 if (k < 0)
                         r = k;
 
@@ -239,21 +293,21 @@ finish:
         return r < 0 ? r : n_found;
 }
 
-static int process_suffix_chop(const char *prefixes, const char *suffix) {
+static int process_suffix_chop(int flags, const char *prefixes, const char *suffix) {
         const char *p;
 
         assert(prefixes);
         assert(suffix);
 
         if (!path_is_absolute(suffix))
-                return process_suffix(prefixes, suffix);
+                return process_suffix(flags, prefixes, suffix);
 
         /* Strip prefix from the suffix */
         NULSTR_FOREACH(p, prefixes) {
                 if (startswith(suffix, p)) {
                         suffix += strlen(p);;
                         suffix += strspn(suffix, "/");
-                        return process_suffix(prefixes, suffix);
+                        return process_suffix(flags, prefixes, suffix);
                 }
         }
 
@@ -267,14 +321,42 @@ static void help(void) {
                "Find overridden configuration files.\n\n"
                "  -h --help           Show this help\n"
                "     --version        Show package version\n"
-               "     --no-pager       Do not pipe output into a pager\n",
+               "     --no-pager       Do not pipe output into a pager\n"
+               "     --diff[=1|0]     Show a diff when overriden files differ\n"
+               "  -t --type=LIST...   Only display a selected set of override types\n",
                program_invocation_short_name);
 }
 
-static int parse_argv(int argc, char *argv[]) {
+static int parse_flags(int flags, const char *flag_str) {
+        char *w, *state;
+        size_t l;
+
+        FOREACH_WORD(w, l, flag_str, state) {
+                if (strncmp("masked", w, l) == 0) {
+                        flags |= SHOW_MASKED;
+                } else if (strncmp ("equivalent", w, l) == 0) {
+                        flags |= SHOW_EQUIV;
+                } else if (strncmp("redirected", w, l) == 0) {
+                        flags |= SHOW_REDIR;
+                } else if (strncmp("override", w, l) == 0) {
+                        flags |= SHOW_OVERRIDEN;
+                } else if (strncmp("unchanged", w, l) == 0) {
+                        flags |= SHOW_UNCHANGED;
+                } else if (strncmp("default", w, l) == 0) {
+                        flags |= SHOW_DEFAULTS;
+                } else {
+                        log_error("Unknown type filter: %s", w);
+                        return -1;
+                }
+        }
+        return flags;
+}
+
+static int parse_argv(int argc, char *argv[], int *flags) {
 
         enum {
                 ARG_NO_PAGER = 0x100,
+                ARG_DIFF,
                 ARG_VERSION
         };
 
@@ -282,6 +364,8 @@ static int parse_argv(int argc, char *argv[]) {
                 { "help",      no_argument,       NULL, 'h'          },
                 { "version",   no_argument,       NULL, ARG_VERSION  },
                 { "no-pager",  no_argument,       NULL, ARG_NO_PAGER },
+                { "diff",      optional_argument, NULL, ARG_DIFF     },
+                { "type",      required_argument, NULL, 't'          },
                 { NULL,        0,                 NULL, 0            }
         };
 
@@ -311,6 +395,23 @@ static int parse_argv(int argc, char *argv[]) {
                 case '?':
                         return -EINVAL;
 
+                case 't':
+                        *flags = parse_flags(*flags, optarg);
+                        if (*flags < 0)
+                                return -EINVAL;
+                        break;
+
+                case ARG_DIFF:
+                        if (!optarg) {
+                                *flags |= SHOW_DIFF;
+                        } else {
+                                if (parse_boolean(optarg))
+                                        *flags |= SHOW_DIFF;
+                                else
+                                        *flags &= ~SHOW_DIFF;
+                        }
+                        break;
+
                 default:
                         log_error("Unknown option code %c", c);
                         return -EINVAL;
@@ -348,14 +449,20 @@ int main(int argc, char *argv[]) {
 
         int r = 0, k;
         int n_found = 0;
+        int flags = 0;
 
         log_parse_environment();
         log_open();
 
-        r = parse_argv(argc, argv);
+        r = parse_argv(argc, argv, &flags);
         if (r <= 0)
                 goto finish;
 
+        if (flags == 0)
+                flags = SHOW_DEFAULTS;
+        if (flags == SHOW_DIFF)
+                flags |= SHOW_OVERRIDEN;
+
         if (!arg_no_pager)
                 pager_open();
 
@@ -363,7 +470,7 @@ int main(int argc, char *argv[]) {
                 int i;
 
                 for (i = optind; i < argc; i++) {
-                        k = process_suffix_chop(prefixes, argv[i]);
+                        k = process_suffix_chop(flags, prefixes, argv[i]);
                         if (k < 0)
                                 r = k;
                         else
@@ -374,7 +481,7 @@ int main(int argc, char *argv[]) {
                 const char *n;
 
                 NULSTR_FOREACH(n, suffixes) {
-                        k = process_suffix(prefixes, n);
+                        k = process_suffix(flags, prefixes, n);
                         if (k < 0)
                                 r = k;
                         else