[PATCH/RFC 1/1] read-cache: optimize file size change when conversion is active

[tboegi@web.de]

From: Torsten Bögershausen <tboegi@web.de>

Commit
"read-cache: do not trust a size change when conversion is active"

corrected the case when the file size in the worktree has changed.
Input filters may convert worktree files with different sizes into the
same blob.

Optimize the new code:
The call to would_convert_to_git() can be skipped since the same check
is done in ce_compare_data()  for regular files, which is called from
ce_modified_check_fs().

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
---
 read-cache.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/read-cache.c b/read-cache.c
index 70f4787de9..3497997bda 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -9,7 +9,6 @@
 
 #include "git-compat-util.h"
 #include "config.h"
-#include "convert.h"
 #include "date.h"
 #include "diff.h"
 #include "diffcore.h"
@@ -456,13 +455,12 @@ int ie_modified(struct index_state *istate,
 		return changed;
 
 	/*
-	 * Immediately after read-tree or update-index --cacheinfo,
-	 * the length field is zero, as we have never even read the
-	 * lstat(2) information once, and we cannot trust DATA_CHANGED
-	 * returned by ie_match_stat() which in turn was returned by
-	 * ce_match_stat_basic() to signal that the filesize of the
-	 * blob changed.  We have to actually go to the filesystem to
-	 * see if the contents match, and if so, should answer "unchanged".
+	 * When the length field of a regular file is zero or changed,
+	 * this does not necessarily mean a changed blob in the index.
+	 * All input filters (CRLF line endings, clean filter..)
+	 * need to be applied followed by a hash and oideq().
+	 * This is done in ce_modified_check_fs() below,
+	 * which calls ce_compare_data().
 	 *
 	 * The logic does not apply to gitlinks, as ce_match_stat_basic()
 	 * already has checked the actual HEAD from the filesystem in the
@@ -479,10 +477,9 @@ int ie_modified(struct index_state *istate,
 	     * So let's just special-case symlinks with a target path length
 	     * (i.e. `sd_size`) of 4096 and force them to be re-checked.
 	     */
-	    (!S_ISLNK(st->st_mode) || ce->ce_stat_data.sd_size != MAX_PATH) &&
+	    (ce->ce_stat_data.sd_size != MAX_PATH) &&
 #endif
-	    (S_ISGITLINK(ce->ce_mode) || ce->ce_stat_data.sd_size != 0) &&
-	    !(S_ISREG(st->st_mode) && would_convert_to_git(istate, ce->name)))
+	    (S_ISGITLINK(ce->ce_mode)))
 		return changed;
 
 	changed_fs = ce_modified_check_fs(istate, ce, st);
-- 
2.53.0.154.g7c02d39fc2