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(dump_file0): The conditional at line

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1296 prevented incremental backups on individual files
from working, as reported by Andreas Schuldei
<andreas@schuldei.org>.

This is due to the condition

  (0 < top_level || !incremental_option)

Removing it makes incremental backups work for individual
files as well as for directories. On the other hand, it does
not affect other functionality, as shown by the reasoning below:

To begin with, the two parts of this condition are mutually
superfluous, because

  1) when top_level < 0, incremental_option == 1
  so the condition yields false
  2) when top_level >= 0, incremental_option == 0
  so the condition yields true.

In other words, it is completely equivalent to

      (!incremental_option)

Now, let's consider the effect of its removal. There are two cases:

1) when incremental_option==1
This means incremental backup in progress. In this case dump_file
is invoked only for directories or for files marked with 'Y' by
get_directory_contents. The latter are those that did not meet the
condition in incremen.c:242, which is exactly the same condition
as this at create.c:1296. So, for these files the check
(!incremental_option) is useless, since the rest of the
conditional will yield false anyway. On the other hand, if
dump_file is invoked on a directory, the conditional will yield
false due to !S_ISDIR assertion, so these will be processed as usual.

Thus, for this case the extra condition (!incremental_option) is
irrelevant, and its removal won't alter the behavior of tar,
*except* that it will enable incremental backups on individual
files, which is the wanted effect.

2) when incremental_option==0
In this case the condition yields true and its removal does not
affect the functionality.
This commit is contained in:
Sergey Poznyakoff
2004-02-21 09:33:58 +00:00
parent ccaedb6b29
commit b960c38c4b
1 changed files with 4 additions and 5 deletions
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9
src/create.c
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@@ -972,8 +972,8 @@ dump_dir0 (char *directory,
return; return;
if (one_file_system_option if (one_file_system_option
&& !top_level && !top_level
&& parent_device != stat->stat.st_dev) && parent_device != stat->stat.st_dev)
{ {
if (verbose_option) if (verbose_option)
WARN ((0, 0, WARN ((0, 0,
@@ -1293,12 +1293,11 @@ dump_file0 (struct tar_stat_info *stat, char *p,
/* See if we want only new files, and check if this one is too old to /* See if we want only new files, and check if this one is too old to
put in the archive. */ put in the archive. */
if ((0 < top_level || !incremental_option) if (!S_ISDIR (stat->stat.st_mode)
&& !S_ISDIR (stat->stat.st_mode)
&& stat->stat.st_mtime < newer_mtime_option && stat->stat.st_mtime < newer_mtime_option
&& (!after_date_option || stat->stat.st_ctime < newer_ctime_option)) && (!after_date_option || stat->stat.st_ctime < newer_ctime_option))
{ {
if (0 < top_level) if (0 < top_level) /* equivalent to !incremental_option */
WARN ((0, 0, _("%s: file is unchanged; not dumped"), WARN ((0, 0, _("%s: file is unchanged; not dumped"),
quotearg_colon (p))); quotearg_colon (p)));
/* FIXME: recheck this return. */ /* FIXME: recheck this return. */