Indentation of multi-line values in text templates

Hi Gwendal

What is the best approach for trying to preserve newline formatting and indentation when processing text (as opposed to HTML) templates?

As a practical example consider the following text template that generates a C file to echo its inputs:

```
#include

int main(int argc, char *argv[])
{

{{ task-input-variables }}
{{ task-input-result }}
return 0;
}
```

The minimal template variable dict for this is:

```
{
"task-input-result" : "\t\/\/ Return inputs as task result\n\tprintf(\"%s\\n\", taskInput1);\n\tprintf(\"%s\\n\", taskInput2);\n\t",
"task-input-variables" : "\t\/\/ Task input variables \n\tchar *taskInput1 = argv[1];\n\tchar *taskInput2 = argv[2];\n"
}
```

The output is :

```
#include

int main(int argc, char *argv[])
{

// Task input variables
char *taskInput1 = argv[1];
char *taskInput2 = argv[2];

// Return inputs as task result
printf("%s\n", taskInput1);
printf("%s\n", taskInput2);

return 0;
}
```

So the above works. However the issues are that I have pre-empt indentation and new line creation. So I have to embed tabs in my variables (otherwise only the first line of say `{{ task-input-variables }}` will be indented) which is less than desirable. What this boils down to is that I would like to be able to format my template as below while maintaining the final rendering shown above.

```
#include

int main(int argc, char *argv[])
{

{{ task-input-variables }}

{{ task-input-result }}

return 0;
}
```

Any thoughts?

Review the issue examples and its 11-comment thread first; no implementation file or test is named. Trace the text-template rendering entry point and define done as applying template indentation to every line of a multiline value while preserving the shown C output.

Written by the indexing model from the issue text.