On Fri, Aug 07, 2020 at 01:05:51AM +0000, Nuthan Munaiah wrote: > * Clone https://github.com/apache/tomcat > * Run `git blame --root -leftw -L 21,21 -L 23,23 > 51844327d8613448bb0bf9667e1a61e462e2043c^ -- > modules/jdbc-pool/java/org/apache/tomcat/jdbc/pool/PoolProperties.java` > > [...] > > `git blame` shows the last commit that modified lines 21 and 23 of > `modules/jdbc-pool/java/org/apache/tomcat/jdbc/pool/PoolProperties.java` > starting at the parent of `51844327d8613448bb0bf9667e1a61e462e2043c`. > > [...] > > Line 23 is not shown in the `git blame` output. Instead, line 22 is shown. Thanks for providing an easy reproduction case. I think the issue is not in the -L input or in the blame algorithm itself, but in the hunk-coalescing at the end. As you note, this shows up even with --porcelain: $ commit=51844327d8613448bb0bf9667e1a61e462e2043c^ $ fn=modules/jdbc-pool/java/org/apache/tomcat/jdbc/pool/PoolProperties.java $ git blame --porcelain -L 21,21 -L 23,23 $commit -- $fn | egrep '^[0-9a-f]{40}' c65a429f06f4e4a025a306e377211863d9ff2a0c 21 21 2 c65a429f06f4e4a025a306e377211863d9ff2a0c 22 22 but if we try --incremental: $ git blame --incremental -L 21,21 -L 23,23 $commit -- $fn | egrep '^[0-9a-f]{40}' c65a429f06f4e4a025a306e377211863d9ff2a0c 21 21 1 c65a429f06f4e4a025a306e377211863d9ff2a0c 22 23 1 So we do know at the moment we find the line that it was at line 23 in the final result, but line 22 in the earlier version at c65a429f06. And indeed, running a non-incremental blame in a debugger, right before calling blame_coalesce() our entries look like this: cmd_blame (argc=3, argv=0x7fffffffe458, prefix=0x0) at builtin/blame.c:1146 1146 blame_coalesce(&sb); (gdb) print *sb->ent $44 = {next = 0x55555596eda0, lno = 20, num_lines = 1, suspect = 0x555555999a30, s_lno = 20, score = 0, ignored = 0, unblamable = 0} (gdb) print *sb->ent->next $45 = {next = 0x0, lno = 22, num_lines = 1, suspect = 0x555555999a30, s_lno = 21, score = 0, ignored = 0, unblamable = 0} So we have two one-line entries at lines 21 and 23 ("lno"; note that internally we zero-index the lines), and we know that the second one is actually from 22 ("s_lno"). But then after blame_coalesce() returns, we have only one entry with both lines: (gdb) n 1148 if (!(output_option & (OUTPUT_COLOR_LINE | OUTPUT_SHOW_AGE_WITH_COLOR))) (gdb) print *sb->ent $46 = {next = 0x0, lno = 20, num_lines = 2, suspect = 0x555555999a30, s_lno = 20, score = 0, ignored = 0, unblamable = 0} Presumably it saw the adjacent lines in the _source_ file and coalesced them, but that's not the right thing to do. They're distinct hunks in the output we're going to show, so they have to remain such. -Peff
