Bug#490374: Please add "describe tag" command-line option

[Chris Lamb <chris@chris-lamb.co.uk>]

Package: lintian
Version: 1.24.1
Severity: wishlist
Tags: patch

It would be nice if lintian had a command-line option to print a tag's
description on-demand. I often come across a tag's name in a build-log or
elsewhere and I find myself running:

  % grep tag-name-here /usr/share/lintian/collection/*.desc

and then opening the file to view the long description. I am aware of the
"--info" flag, but this only helps if you are controlling the lintian run.

Patch attached.


Regards,

-- 
Chris Lamb, UK                                       chris@chris-lamb.co.uk
                                                            GPG: 0x634F9A20

diff --git a/frontend/lintian b/frontend/lintian
index 1be2e9b..25e24b4 100755
--- a/frontend/lintian
+++ b/frontend/lintian
@@ -80,6 +80,7 @@ my $unpack_info;
 my $cwd;
 my $cleanup_filename;
 my $exit_code = 0;
+my $describe_tag;
 my $LAB;
 
 my %collection_info;
@@ -130,6 +131,7 @@ Actions:
     -X X, --dont-check-part X don\'t check certain aspects
     -u, --unpack              only unpack packages in the lab
     -r, --remove              remove package from the lab
+    -D X, --describe X        print description of a tag and then exit
 General options:
     -h, --help                display short help text
     -v, --verbose             verbose messages
@@ -221,6 +223,18 @@ sub record_dont_check_part {
     $dont_check = "$_[1]";
 }
 
+# Record describe option
+# Options: -D|--describe
+sub record_describe {
+    if (defined $action and $action eq 'describe' and $describe_tag) {
+	die("multiple -D or --describe options not allowed");
+    }
+    if ($action) {
+	die("too many actions specified: $_[0]");
+    }
+    $action = 'describe';
+    $describe_tag = "$_[1]";
+}
 
 # Process for -U|--unpack-info flag
 sub record_unpack_info {
@@ -247,6 +261,7 @@ my %opthash = (			# ------------------ actions
 	       "dont-check-part|X=s" => \&record_dont_check_part,
 	       "unpack|u" => \&record_action,
 	       "remove|r" => \&record_action,
+	       "describe|D=s" => \&record_describe,
 
 	       # ------------------ general options
 	       "help|h" => \&syntax,
@@ -575,6 +590,13 @@ if ($action eq 'setup-lab') {
     exit 0;
 
 #######################################
+# Process -D option
+} elsif ($action eq 'describe') {
+    if ($#ARGV+1 > 0) {
+	die("Cannot specify -D|--describe and additional command line arguments.\n");
+    }
+
+#######################################
 #  Check for non deb specific actions
 } elsif (not (($action eq 'unpack') or ($action eq 'check')
 	      or ($action eq 'remove'))) {
@@ -880,7 +902,8 @@ while (my $arg = shift) {
     }
 }
 
-if (not $check_everything and not $packages_file and ($#packages == -1)) {
+if (not $check_everything and not $packages_file and ($#packages == -1)
+	and ($action ne "describe")) {
     print "N: No packages selected.\n" if $verbose;
     exit $exit_code;
 }
@@ -1053,11 +1076,27 @@ for my $f (readdir CHECKDIR) {
 	}
 
 	shift(@secs);
-	map Tags::add_tag($_), @secs;
+
+	if ($action eq "describe") {
+	    for my $sec (@secs) {
+	        if ($sec->{'tag'} eq $describe_tag) {
+	            for (qw(tag type info ref)) {
+	                print ucfirst($_) . ": $sec->{$_}\n";
+	            }
+	            exit 0;
+	        }
+	    }
+	} else {
+	    map Tags::add_tag($_), @secs;
+	}
     } # end: if ne lintian
 
 }
 
+if ($action eq 'describe') {
+    die("Tag \"$describe_tag\" not found.\n");
+}
+
 closedir(CHECKDIR);
 
 # }}}
diff --git a/man/lintian.1 b/man/lintian.1
index 6d0d76b..0e85108 100644
--- a/man/lintian.1
+++ b/man/lintian.1
@@ -105,6 +105,10 @@ Clean up the lintian directory of the specified packages up to
 the current unpack level.  The default unpack level is 0 for
 this option.
 
+.TP
+.BR \-D " tag, " \-\-describe " tag "
+Print a description of the specified tag and then exit.
+
 .PP
 General options:

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