unpack-trees: allow Porcelain to give different error messages

diff --git a/xdiff-interface.c b/xdiff-interface.c
index 69a022c134e422abe7c9c1888f59332797ba1eba..61dc5c547019776b971dc89d009f628bbac134fd 100644 (file)
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -103,9 +103,42 @@ int xdiff_outf(void *priv_, mmbuffer_t *mb, int nbuf)
        return 0;
 }
 
+/*
+ * Trim down common substring at the end of the buffers,
+ * but leave at least ctx lines at the end.
+ */
+static void trim_common_tail(mmfile_t *a, mmfile_t *b, long ctx)
+{
+       const int blk = 1024;
+       long trimmed = 0, recovered = 0;
+       char *ap = a->ptr + a->size;
+       char *bp = b->ptr + b->size;
+       long smaller = (a->size < b->size) ? a->size : b->size;
+
+       if (ctx)
+               return;
+
+       while (blk + trimmed <= smaller && !memcmp(ap - blk, bp - blk, blk)) {
+               trimmed += blk;
+               ap -= blk;
+               bp -= blk;
+       }
+
+       while (recovered < trimmed)
+               if (ap[recovered++] == '\n')
+                       break;
+       a->size -= trimmed - recovered;
+       b->size -= trimmed - recovered;
+}
+
 int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *xecb)
 {
-       return xdl_diff(mf1, mf2, xpp, xecfg, xecb);
+       mmfile_t a = *mf1;
+       mmfile_t b = *mf2;
+
+       trim_common_tail(&a, &b, xecfg->ctxlen);
+
+       return xdl_diff(&a, &b, xpp, xecfg, xecb);
 }
 
 int read_mmfile(mmfile_t *ptr, const char *filename)
@@ -119,8 +152,8 @@ int read_mmfile(mmfile_t *ptr, const char *filename)
        if ((f = fopen(filename, "rb")) == NULL)
                return error("Could not open %s", filename);
        sz = xsize_t(st.st_size);
-       ptr->ptr = xmalloc(sz);
-       if (fread(ptr->ptr, sz, 1, f) != 1)
+       ptr->ptr = xmalloc(sz ? sz : 1);
+       if (sz && fread(ptr->ptr, sz, 1, f) != 1)
                return error("Could not read %s", filename);
        fclose(f);
        ptr->size = sz;
@@ -200,8 +233,7 @@ void xdiff_set_find_func(xdemitconf_t *xecfg, const char *value)
                        expression = value;
                if (regcomp(&reg->re, expression, 0))
                        die("Invalid regexp to look for hunk header: %s", expression);
-               if (buffer)
-                       free(buffer);
+               free(buffer);
                value = ep + 1;
        }
 }