apply --whitespace=warn/error: diagnose blank at EOF

"git apply" strips new blank lines at EOF under --whitespace=fix option,
but neigher --whitespace=warn nor --whitespace=error paid any attention to
these errors.

Introduce a new whitespace error class, blank-at-eof, to make the
whitespace error handling more consistent.

The patch adds a new "linenr" field to the struct fragment in order to
record which line the hunk started in the input file, but this is needed
solely for reporting purposes.  The detection of this class of whitespace
errors cannot be done while parsing a patch like we do for all the other
classes of whitespace errors.  It instead has to wait until we find where
to apply the hunk, but at that point, we do not have an access to the
original line number in the input file anymore, hence the new field.

Depending on your point of view, this may be a bugfix that makes warn and
error in line with fix.  Or you could call it a new feature.  The line
between them is somewhat fuzzy in this case.

Strictly speaking, triggering more errors than before is a change in
behaviour that is not backward compatible, even though the reason for the
change is because the code was not checking for an error that it should
have.  People who do not want added blank lines at EOF to trigger an error
can disable the new error class.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/cache.h b/cache.h
index 099a32e5fc..7152feaef2 100644
--- a/cache.h
+++ b/cache.h
@@ -845,7 +845,8 @@ void shift_tree(const unsigned char *, const unsigned char *, unsigned char *, i
 #define WS_SPACE_BEFORE_TAB	02
 #define WS_INDENT_WITH_NON_TAB	04
 #define WS_CR_AT_EOL           010
-#define WS_DEFAULT_RULE (WS_TRAILING_SPACE|WS_SPACE_BEFORE_TAB)
+#define WS_BLANK_AT_EOF        020
+#define WS_DEFAULT_RULE (WS_TRAILING_SPACE|WS_SPACE_BEFORE_TAB|WS_BLANK_AT_EOF)
 extern unsigned whitespace_rule_cfg;
 extern unsigned whitespace_rule(const char *);
 extern unsigned parse_whitespace_rule(const char *);