Update why unified diff is _sometimes_ better.

Author: bmomjian

doc/FAQ_DEV

@@ -1,7 +1,7 @@
 
           Developer's Frequently Asked Questions (FAQ) for PostgreSQL
 
-   Last updated: Tue Nov 22 10:17:51 EST 2005
+   Last updated: Sat Dec 24 13:36:54 EST 2005
 
    Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
 
@@ -110,7 +110,8 @@ General Questions
 
    Generate the patch in contextual diff format. If you are unfamiliar
    with this, you might find the script src/tools/makediff/difforig
-   useful.
+   useful. Unified diffs are only preferrable if the file changes are
+   single-line changes and do not rely on the surrouding lines.
 
    Ensure that your patch is generated against the most recent version of
    the code. If it is a patch adding new functionality, the most recent

doc/src/FAQ/FAQ_DEV.html

@@ -13,7 +13,7 @@
     <H1>Developer's Frequently Asked Questions (FAQ) for
     PostgreSQL</H1>
 
-    <P>Last updated: Tue Nov 22 10:17:51 EST 2005</P>
+    <P>Last updated: Sat Dec 24 13:36:54 EST 2005</P>
 
     <P>Current maintainer: Bruce Momjian (<A href=
     "mailto:pgman@candle.pha.pa.us">pgman@candle.pha.pa.us</A>)<BR>
@@ -158,7 +158,9 @@ <H3 id="item1.5">1.5) I've developed a patch, what next?</H3>
 
     <P>Generate the patch in contextual diff format. If you are
     unfamiliar with this, you might find the script
-    <I>src/tools/makediff/difforig</I> useful.</P>
+    <I>src/tools/makediff/difforig</I> useful.  Unified diffs are
+    only preferrable if the file changes are single-line changes and
+    do not rely on the surrouding lines.</P>
 
     <P>Ensure that your patch is generated against the most recent
     version of the code. If it is a patch adding new functionality, the