Revert (almost) to the original asymmetric hunk behavior and document that

5 files changed, 30 insertions, 23 deletions

diff --git a/ChangeLog b/ChangeLog
index 6b0a63f..6a6248a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -65,6 +65,13 @@
 	that keepeing them here as introduced.
 	* tests/backup-prefix-suffix: Add more regression tests.
 
+	* src/patch.c (locate_hunk): Revert to the original asymmetric hunk
+	behavior (but only anchor hunks starting at line 0 to the start of the
+	file): there is not enough reason to change the historic behavior.
+	* tests/asymmetric-hunks: Update accordingly.
+	* patch.man: Document the asymmetric hunk behavior.
+	* NEWS: Update.
+
 2009-04-04  Andreas Gruenbacher  <agruen@suse.de>
 
 	* pch.c (another_hunk): Add (back) the line number ranges to the
diff --git a/NEWS b/NEWS
index 8874d97..6144684 100644
--- a/NEWS
+++ b/NEWS
@@ -32,9 +32,6 @@
   line endings in patches.  This allows to preserve CRs even in mangled
   patches, or in patches generated without the --binary option on non-POSIX
   systems.
-* Hunks with a different number of lines in the prefix and suffix context
-  can now apply anywhere in the file, rather than only at the beginning
-  (shorter prefix context) or at the end (shorter suffix context).
 * Backup files for nonexisting files are now created with default
   permissions rather than with mode 0: backup files with mode 0 were
   causing problems with applications which do not expect unreadable
@@ -43,12 +40,6 @@
   imply the simple version control mode, and can be combined.
 * Reject more malformed normal format commands and check for trailing
   garbage.  Recognize ed commands without addresses.
-* As seemingly originally intended, patch will assume that hunks with fewer
-  lines of prefix than suffix context which start at line 1 must apply at the
-  beginning of the file, while hunks with fewer lines of suffix context must
-  apply at the end of the file.  If a high-enough fuzz factor is allowed to
-  strip off all context (which is not the default), such hunks can also apply
-  within a file.
 * Handle missing timestamps better.
 * Various bug fixes.
 
diff --git a/patch.man b/patch.man
index fc95e2b..1f71a4e 100644
--- a/patch.man
+++ b/patch.man
@@ -94,6 +94,12 @@ If that fails, and the maximum fuzz factor is set to 2 or more,
 the first two and last two lines of context are ignored,
 and another scan is made.
 (The default maximum fuzz factor is 2.)
+.PP
+Hunks with less prefix context than suffix context (after applying fuzz)
+must apply at the start of the file if their first line number is\ 1.  Hunks
+with more prefix context than suffix context (after applying fuzz) must apply
+at the end of the file.
+.PP
 If
 .B patch
 cannot find a place to install that hunk of the patch, it puts the
diff --git a/src/patch.c b/src/patch.c
index d8c7390..e197741 100644
--- a/src/patch.c
+++ b/src/patch.c
@@ -900,8 +900,10 @@ locate_hunk (LINENUM fuzz)
     LINENUM pat_lines = pch_ptrn_lines();
     LINENUM prefix_context = pch_prefix_context ();
     LINENUM suffix_context = pch_suffix_context ();
-    LINENUM prefix_fuzz = (prefix_context < fuzz ? prefix_context : fuzz);
-    LINENUM suffix_fuzz = (suffix_context < fuzz ? suffix_context : fuzz);
+    LINENUM context = (prefix_context < suffix_context
+		       ? suffix_context : prefix_context);
+    LINENUM prefix_fuzz = fuzz + prefix_context - context;
+    LINENUM suffix_fuzz = fuzz + suffix_context - context;
     LINENUM max_where = input_lines - (pat_lines - suffix_fuzz) + 1;
     LINENUM min_where = last_frozen_line + 1 - (prefix_context - prefix_fuzz);
     LINENUM max_pos_offset = max_where - first_guess;
@@ -916,8 +918,7 @@ locate_hunk (LINENUM fuzz)
     if (first_guess <= max_neg_offset)
 	max_neg_offset = first_guess - 1;
 
-    if (prefix_context < suffix_context && fuzz < suffix_context
-	&& pch_first () <= 1)
+    if (prefix_fuzz < 0 && pch_first () <= 1)
       {
 	/* Can only match start of file.  */
 
@@ -937,8 +938,10 @@ locate_hunk (LINENUM fuzz)
 	else
 	  return 0;
       }
+    else if (prefix_fuzz < 0)
+      prefix_fuzz = 0;
 
-    if (suffix_context < prefix_context && fuzz < prefix_context)
+    if (suffix_fuzz < 0)
       {
 	/* Can only match end of file.  */
 	offset = first_guess - (input_lines - pat_lines + 1);
diff --git a/tests/asymmetric-hunks b/tests/asymmetric-hunks
index 83fb06d..da85024 100644
--- a/tests/asymmetric-hunks
+++ b/tests/asymmetric-hunks
@@ -13,8 +13,8 @@ use_tmpdir
 
 # ==============================================================
 
-# Starts at a line <= 1 and prefix context < suffix context: start of file
-# until all context has been stripped.
+# Starts at a line <= 1 and prefix context < suffix context: start of
+# file until hunk has become symmetric.
 
 cat > a.diff <<EOF
 --- a
@@ -30,7 +30,7 @@ seq 1 5 > a
 
 check 'patch < a.diff' <<EOF
 patching file a
-Hunk #1 succeeded at 1 with fuzz 2.
+Hunk #1 succeeded at 2 with fuzz 1 (offset 1 line).
 EOF
 
 seq 2 5 > a
@@ -53,17 +53,17 @@ cat > a.diff <<EOF
  4
 EOF
 
-# ==============================================================
-
-# Prefix context > suffix context: en dof file until all context has been
-# stripped.
-
 seq 1 5 > a
 
 check 'patch < a.diff' <<EOF
 patching file a
 EOF
 
+# ==============================================================
+
+# Prefix context > suffix context: end of file until hunk has
+# become symmetric.
+
 cat > a.diff <<EOF
 --- a
 +++ a
@@ -78,5 +78,5 @@ seq 1 5 > a
 
 check 'patch < a.diff' <<EOF
 patching file a
-Hunk #1 succeeded at 2 with fuzz 2.
+Hunk #1 succeeded at 2 with fuzz 1.
 EOF