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Re: [PATCH] rebase -x: sanity check command




Hi Dscho

On 28/01/2019 22:03, Johannes Schindelin wrote:
> Hi Phillip,
> 
> On Mon, 28 Jan 2019, Phillip Wood wrote:
> 
>> From: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
>>
>> If the user gives an empty argument to --exec then the rebase starts to
>> run before erroring out with
>>
>>   error: missing arguments for exec
>>   error: invalid line 2: exec
>>   You can fix this with 'git rebase --edit-todo' and then run 'git rebase --continue'.
>>   Or you can abort the rebase with 'git rebase --abort'.
> 
> And that's the same if you specify an incorrect command.

Not quite, the issue is that the todo list is invalid, not that the
command fails - it never gets that far. Those errors are coming from
parse_insn_line() and parse_insn_buffer().

> 
> In both cases, I would probably heed the second line of the advice: git
> rebase --abort.
> 
>> Instead check for empty commands before starting the rebase.
>>
>> Also check that the command does not contain any newlines as the
>> todo-list format is unable to cope with multiline commands. Note that
>> this changes the behavior, before this change one could do
>>
>> git rebase --exec='echo one
>> exec echo two'
>>
>> and it would insert two exec lines in the todo list, now it will error
>> out.
> 
> This, however, makes a ton of sense to me.
> 
>> diff --git a/builtin/rebase.c b/builtin/rebase.c
>> index 00de70365e..b6c54b03c1 100644
>> --- a/builtin/rebase.c
>> +++ b/builtin/rebase.c
>> @@ -793,6 +793,24 @@ static void set_reflog_action(struct rebase_options *options)
>>  	strbuf_release(&buf);
>>  }
>>  
>> +static int check_exec_cmd(const char *cmd)
>> +{
>> +	int non_blank = 0;
>> +
>> +	while (*cmd) {
>> +		if (*cmd == '\n')
>> +			return error(_("exec commands cannot contain newlines"));
>> +		if (!isspace(*cmd))
>> +			non_blank = 1;
>> +		cmd++;
>> +	}
>> +
>> +	if (non_blank)
>> +		return 0;
> 
> We are not in a performance critical path here, so I would prefer the
> readability of this code:
> 
> 	if (strchr(cmd, '\n'))
> 		return error(...);
> 
> And if you *really* must,
> 
> 	/* Does the command consist purely of whitespace? */
> 	if (!cmd[strspn(cmd, " \t\r\n")])
> 		return error(...);
> 
> But as I suggested also in a reply to Junio's answer: where would we stop
> to validate the commands?

I'm not trying to validate the command (and I don't think we can/should)
- just generate a todo list that can be parsed.

Best Wishes

Phillip

> 
> Ciao,
> Dscho
> 
>> +
>> +	return error(_("empty exec command"));
>> +}
>> +
>>  int cmd_rebase(int argc, const char **argv, const char *prefix)
>>  {
>>  	struct rebase_options options = {
>> @@ -1130,6 +1148,10 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
>>  		}
>>  	}
>>  
>> +	for (i = 0; i < exec.nr; i++)
>> +		if (check_exec_cmd(exec.items[i].string))
>> +			exit(1);
>> +
>>  	if (!(options.flags & REBASE_NO_QUIET))
>>  		argv_array_push(&options.git_am_opts, "-q");
>>  
>> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
>> index 7a440e08d8..c98f64eb2d 100755
>> --- a/t/t3404-rebase-interactive.sh
>> +++ b/t/t3404-rebase-interactive.sh
>> @@ -147,6 +147,25 @@ test_expect_success 'rebase -i with the exec command checks tree cleanness' '
>>  	git rebase --continue
>>  '
>>  
>> +test_expect_success 'rebase -x with empty command fails' '
>> +	test_when_finished "git rebase --abort ||:" &&
>> +	test_must_fail git rebase -x "" @ 2>actual &&
>> +	test_write_lines "error: empty exec command" >expected &&
>> +	test_i18ncmp expected actual &&
>> +	test_must_fail git rebase -x " " @ 2>actual &&
>> +	test_i18ncmp expected actual
>> +'
>> +
>> +LF='
>> +'
>> +test_expect_success 'rebase -x with newline in command fails' '
>> +	test_when_finished "git rebase --abort ||:" &&
>> +	test_must_fail git rebase -x "a${LF}b" @ 2>actual &&
>> +	test_write_lines "error: exec commands cannot contain newlines" \
>> +			 >expected &&
>> +	test_i18ncmp expected actual
>> +'
>> +
>>  test_expect_success 'rebase -i with exec of inexistent command' '
>>  	git checkout master &&
>>  	test_when_finished "git rebase --abort" &&
>> -- 
>> 2.20.1
>>
>>