[tz] [PATCH 4/5] Improve checking for shortcut links

[Paul Eggert]

* backward: Add comments for shortcut links.
* checklinks.awk: Check these links.
---
 backward       | 34 ++++++++++++++++++++++------------
 checklinks.awk | 13 +++++++++++++
 2 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/backward b/backward
index f61c260..b2ccbc1 100644
--- a/backward
+++ b/backward
@@ -16,11 +16,21 @@
 # This file is divided into sections, one for each major reason for a
 # backward compatibility link.  Each section is sorted by link name.
 
+# A "#= TARGET1" comment labels each link inserted only because some
+# .zi parsers mishandle links to links.  The comment says what the
+# target would be if these parsers were fixed so that data could
+# contain links to links.  For example, the line
+# "Link Australia/Sydney Australia/ACT #= Australia/Canberra" would be
+# "Link Australia/Canberra Australia/ACT" were it not that data lines
+# refrain from linking to links like Australia/Canberra, which means
+# the Australia/ACT line links instead to Australia/Sydney,
+# Australia/Canberra's target.
+
 
 # Pre-1993 naming conventions
 
-# Link	TARGET			LINK-NAME
-Link	Australia/Sydney	Australia/ACT
+# Link	TARGET			LINK-NAME	#= TARGET1
+Link	Australia/Sydney	Australia/ACT	#= Australia/Canberra
 Link	Australia/Lord_Howe	Australia/LHI
 Link	Australia/Sydney	Australia/NSW
 Link	Australia/Darwin	Australia/North
@@ -30,7 +40,7 @@ Link	Australia/Hobart	Australia/Tasmania
 Link	Australia/Melbourne	Australia/Victoria
 Link	Australia/Perth		Australia/West
 Link	Australia/Broken_Hill	Australia/Yancowinna
-Link	America/Rio_Branco	Brazil/Acre
+Link	America/Rio_Branco	Brazil/Acre	#= America/Porto_Acre
 Link	America/Noronha		Brazil/DeNoronha
 Link	America/Sao_Paulo	Brazil/East
 Link	America/Manaus		Brazil/West
@@ -79,7 +89,7 @@ Link	Etc/GMT			GMT0
 Link	Etc/GMT			Greenwich
 # End of rearguard section.
 Link	Asia/Hong_Kong		Hongkong
-Link	Africa/Abidjan		Iceland
+Link	Africa/Abidjan		Iceland	#= Atlantic/Reykjavik
 Link	Asia/Tehran		Iran
 Link	Asia/Jerusalem		Israel
 Link	America/Jamaica		Jamaica
@@ -91,7 +101,7 @@ Link	America/Mazatlan	Mexico/BajaSur
 Link	America/Mexico_City	Mexico/General
 Link	Pacific/Auckland	NZ
 Link	Pacific/Chatham		NZ-CHAT
-Link	America/Denver		Navajo
+Link	America/Denver		Navajo	#= America/Shiprock
 Link	Asia/Shanghai		PRC
 Link	Europe/Warsaw		Poland
 Link	Europe/Lisbon		Portugal
@@ -120,7 +130,7 @@ Link	Etc/UTC			Zulu
 
 # Two-part names that were renamed mostly to three-part names in 1995
 
-# Link	TARGET				LINK-NAME
+# Link	TARGET				LINK-NAME	#= TARGET1
 Link	America/Argentina/Buenos_Aires	America/Buenos_Aires
 Link	America/Argentina/Catamarca	America/Catamarca
 Link	America/Argentina/Cordoba	America/Cordoba
@@ -129,7 +139,7 @@ Link	America/Argentina/Jujuy		America/Jujuy
 Link	America/Indiana/Knox		America/Knox_IN
 Link	America/Kentucky/Louisville	America/Louisville
 Link	America/Argentina/Mendoza	America/Mendoza
-Link	America/Puerto_Rico		America/Virgin
+Link	America/Puerto_Rico		America/Virgin	#= America/St_Thomas
 Link	Pacific/Pago_Pago		Pacific/Samoa
 
 
@@ -279,12 +289,12 @@ Link	Pacific/Port_Moresby	Pacific/Yap
 
 # Alternate names for the same location
 
-# Link	TARGET			LINK-NAME
-Link	Africa/Nairobi		Africa/Asmera
+# Link	TARGET			LINK-NAME	#= TARGET1
+Link	Africa/Nairobi		Africa/Asmera	#= Africa/Asmara
 Link	America/Nuuk		America/Godthab
 Link	Asia/Ashgabat		Asia/Ashkhabad
 Link	Asia/Kolkata		Asia/Calcutta
-Link	Asia/Shanghai		Asia/Chungking
+Link	Asia/Shanghai		Asia/Chungking	#= Asia/Chongqing
 Link	Asia/Dhaka		Asia/Dacca
 # Istanbul is in both continents.
 Link	Europe/Istanbul		Asia/Istanbul
@@ -300,5 +310,5 @@ Link	Europe/Kyiv		Europe/Kiev
 # Classically, Cyprus is in Asia; e.g. see Herodotus, Histories, I.72.
 # However, for various reasons many users expect to find it under Europe.
 Link	Asia/Nicosia		Europe/Nicosia
-Link	Pacific/Guadalcanal	Pacific/Ponape
-Link	Pacific/Port_Moresby	Pacific/Truk
+Link	Pacific/Guadalcanal	Pacific/Ponape	#= Pacific/Pohnpei
+Link	Pacific/Port_Moresby	Pacific/Truk	#= Pacific/Chuuk
diff --git a/checklinks.awk b/checklinks.awk
index b2bb17a..6e4fda8 100644
--- a/checklinks.awk
+++ b/checklinks.awk
@@ -36,6 +36,9 @@ BEGIN {
       printf "%s: Link should be in '%s'\n", $3, backcheck
       status = 1
     }
+    if ($4 == "#=") {
+      shortcut[$5] = $3
+    }
     used[$2] = 1
     defined[$3] = $2
 }
@@ -47,6 +50,16 @@ END {
 	    status = 1
 	}
     }
+    for (tz in shortcut) {
+      if (defined[shortcut[tz]] != defined[tz]) {
+	target = (!defined[tz] ? "absence" \
+		  : defined[tz] == "\n" ? "zone" \
+		  : defined[tz])
+	printf "%s: target %s disagrees with %s's target %s\n", \
+	  tz, target, shortcut[tz], defined[shortcut[tz]]
+	status = 1
+      }
+    }
 
     exit status
 }
-- 
2.37.3