xdiff: unignore changes in function context

Changes involving only blank lines are hidden with --ignore-blank-lines,
unless they appear in the context lines of other changes.  This is
handled by xdl_get_hunk() for context added by --inter-hunk-context, -u
and -U.

Function context for -W and --function-context added by xdl_emit_diff()
doesn't pay attention to such ignored changes; it relies fully on
xdl_get_hunk() and shows just the post-image of ignored changes
appearing in function context.  That's inconsistent and confusing.

Improve the result of using --ignore-blank-lines and --function-context
together by fully showing ignored changes if they happen to fall within
function context.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index 6b087df3dcbd01df9c7e533f9e039518beaa773a..4a7254ec5f2e822cf643ab3cfa6434e95cbebd04 100755 (executable)
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -2008,11 +2008,6 @@ test_expect_success 'compare mixed whitespace delta across moved blocks' '
        test_cmp expected actual
 '
 
-# Note that the "6" in the expected hunk header below is funny, since we only
-# show 5 lines (the missing one was blank and thus ignored). This is how
-# --ignore-blank-lines behaves even without --function-context, and this test
-# is just checking the interaction of the two features. Don't take it as an
-# endorsement of that output.
 test_expect_success 'combine --ignore-blank-lines with --function-context' '
        test_write_lines 1 "" 2 3 4 5 >a &&
        test_write_lines 1    2 3 4   >b &&
@@ -2022,6 +2017,7 @@ test_expect_success 'combine --ignore-blank-lines with --function-context' '
        cat <<-\EOF >expect &&
        @@ -1,6 +1,4 @@
         1
+       -
         2
         3
         4

diff --git a/xdiff/xemit.c b/xdiff/xemit.c
index 30713ae9a98ecfc9f764120d3a1d18b5a8ee11bf..9d7d6c5087498a0a9079775cb3b744db69fe807e 100644 (file)
--- a/xdiff/xemit.c
+++ b/xdiff/xemit.c
@@ -172,10 +172,12 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
        struct func_line func_line = { 0 };
 
        for (xch = xscr; xch; xch = xche->next) {
+               xdchange_t *xchp = xch;
                xche = xdl_get_hunk(&xch, xecfg);
                if (!xch)
                        break;
 
+pre_context_calculation:
                s1 = XDL_MAX(xch->i1 - xecfg->ctxlen, 0);
                s2 = XDL_MAX(xch->i2 - xecfg->ctxlen, 0);
 
@@ -212,6 +214,21 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
                        if (fs1 < s1) {
                                s2 = XDL_MAX(s2 - (s1 - fs1), 0);
                                s1 = fs1;
+
+                               /*
+                                * Did we extend context upwards into an
+                                * ignored change?
+                                */
+                               while (xchp != xch &&
+                                      xchp->i1 + xchp->chg1 <= s1 &&
+                                      xchp->i2 + xchp->chg2 <= s2)
+                                       xchp = xchp->next;
+
+                               /* If so, show it after all. */
+                               if (xchp != xch) {
+                                       xch = xchp;
+                                       goto pre_context_calculation;
+                               }
                        }
                }