Document --yet-to-unpack, --predep-packages and --assert-<feature> commands

Both in «dpkg --help» and dpkg(1). Mark them as supported.

Prompted-by: Johannes Schauer <j.schauer@email.de>

debian/changelog

@@ -8,6 +8,8 @@ dpkg (1.18.2) UNRELEASED; urgency=low
     - Use the feature area name in the dpkg-buildflags(1) subsection title.
     - Document DPKG_HOOK_ACTION also in dpkg(1) ENVIRONMENT section.
     - Clarify when some features where added in man pages.
+    - Document --yet-to-unpack, --predep-packages and all --assert-<feature>
+      commands as supported in both «dpkg --help» and dpkg(1).
 
   [ Updated programs translations ]
   * Dutch (Frans Spiesschaert). Closes: #789097

man/dpkg.1

@@ -308,6 +308,16 @@ to deinstall any packages not in list given to \fB\-\-set\-selections\fP.
 Searches for packages selected for installation, but which for some
 reason still haven't been installed.
 .TP
+.B \-\-predep\-packages
+Print a single package which, is the target of one or more relevant
+pre-dependencies, and has itself no unsatisfied pre-dependencies.
+.IP
+If such a package is present, output it as a Packages file entry,
+which can be massaged as appropriate.
+.IP
+Returns 0 when a package is printed, 1 when no suitable package is
+available and 2 on error.
+.TP
 .B \-\-add\-architecture \fIarchitecture\fP
 Add \fIarchitecture\fP to the list of architectures for which packages can
 be installed without using \fB\-\-force\-architecture\fP (since dpkg 1.16.2).
@@ -331,6 +341,32 @@ Print architecture of packages \fBdpkg\fP installs (for example, \(lqi386\(rq).
 Print a newline-separated list of the extra architectures \fBdpkg\fP is
 configured to allow packages to be installed for (since dpkg 1.16.2).
 .TP
+.BI \-\-assert\- feature
+Asserts that \fBdpkg\fP supports the requested feature.
+Returns 0 if the feature is fully supported, 1 if the feature is known but
+\fBdpkg\fP cannot provide support for it yet, and 2 if the feature is unknown.
+The current list of assertable features is:
+.RS
+.TP
+.B support\-predepends
+Supports the \fBPre\-Depends\fP field (since dpkg 1.1.0).
+.TP
+.B working\-epoch
+Supports epochs in version strings (since dpkg 1.4.0.7).
+.TP
+.B long\-filenames
+Supports long filenames in \fBdeb\fP(5) archives (since dpkg 1.4.1.17).
+.TP
+.B multi\-conrep
+Supports multiple \fBConflicts\fP and \fBReplaces\fP (since dpkg 1.4.1.19).
+.TP
+.B multi\-arch
+Supports multi-arch fields and semantics (since dpkg 1.16.2).
+.TP
+.B versioned\-provides
+Supports versioned \fBProvides\fP (since dpkg 1.17.11).
+.RE
+.TP
 .B \-\-compare\-versions \fIver1 op ver2\fP
 Compare version numbers, where \fIop\fP is a binary operator. \fBdpkg\fP
 returns success (zero result) if the specified condition is satisfied,

src/main.c

@@ -71,7 +71,6 @@ printversion(const struct cmdinfo *ci, const char *value)
 
 /*
  * FIXME: Options that need fixing:
- * dpkg --yet-to-unpack
  * dpkg --command-fd
  */
 
@@ -105,10 +104,13 @@ usage(const struct cmdinfo *ci, const char *value)
 "  -l|--list [<pattern> ...]        List packages concisely.\n"
 "  -S|--search <pattern> ...        Find package(s) owning file(s).\n"
 "  -C|--audit [<package> ...]       Check for broken package(s).\n"
+"  --yet-to-unpack                  Print packages selected for installation.\n"
+"  --predep-packages                Print pre-dependencies to unpack.\n"
 "  --add-architecture <arch>        Add <arch> to the list of architectures.\n"
 "  --remove-architecture <arch>     Remove <arch> from the list of architectures.\n"
 "  --print-architecture             Print dpkg architecture.\n"
 "  --print-foreign-architectures    Print allowed foreign architectures.\n"
+"  --assert-<feature>               Assert support for the specified feature.\n"
 "  --compare-versions <a> <op> <b>  Compare version numbers - see below.\n"
 "  --force-help                     Show help on forcing.\n"
 "  -Dh|--debug=help                 Show help on debugging.\n"
@@ -117,6 +119,11 @@ usage(const struct cmdinfo *ci, const char *value)
   printf(_(
 "  -?, --help                       Show this help message.\n"
 "      --version                    Show the version.\n"
+"\n"));
+
+  printf(_(
+"Assertable features: support-predepends, working-epoch, long-filenames,\n"
+"  multi-conrep, multi-arch, versioned-provides.\n"
 "\n"));
 
   printf(_(
@@ -125,12 +132,6 @@ usage(const struct cmdinfo *ci, const char *value)
 "on archives (type %s --help).\n"
 "\n"), BACKEND);
 
-  printf(_(
-"For internal use: dpkg --assert-support-predepends | --predep-package |\n"
-"  --assert-working-epoch | --assert-long-filenames | --assert-multi-conrep |\n"
-"  --assert-multi-arch | --assert-versioned-provides.\n"
-"\n"));
-
   printf(_(
 "Options:\n"
 "  --admindir=<directory>     Use <directory> instead of %s.\n"