autotest: update tests for gdal_calc

[dbaston]

• simplify generation of temporary file names, since they'll be cleaned up automatically
• separate independent tests into separate functions
• add tests for untested arguments
• avoid copying input dataset for every test function
• use vsimem where possible

[coveralls]

coverage: 70.074% (+0.01%) from 70.061%
when pulling 174e822 on dbaston:gdal-calc-tidy
into f41af17 on OSGeo:master.

[dbaston]

Should the @optfile syntax work in Windows CMD? The way the test was written previously, it passed even though the call to gdal_calc failed. I'm trying to figure out if it should succeed. When I call gdal_calc from CMD (outside of the test framework), it appears to strip all of the \ characters from the optfile, causing gdal_calc to fail because it can't find the input dataset.

[rouault]

Should the @optfile syntax work in Windows CMD?

I've no idea. If that's an annoyance, just skip the test on Windows

[jratike80]

Should the @optfile syntax work in Windows CMD?

gdal_calc @optfile.txt
0...10...20...30...40...50...60...70...80...90...100 - done.

Maybe the optfile itself does not work on Windows? Like having \ as newlines, while it maybe should be ^.
I tested with a simple optfile.txt
-A input1.tif -B input2.tif --outfile=result.tif --calc="(A+B)/2"

And if the trouble was caused by the file paths, Windows supports also forward slashes
-A C:/data/000/00/input1.tif -B C:/data/000/00/input2.tif --outfile=C:/data/000/00/result.tif --calc="(A+B)/2"

[dbaston]

Here are the optfile contents:

-A C:\Users\dbaston\AppData\Local\Temp\pytest-of-dbaston\pytest-5\gdal_calc0\stefan_full_rgba.tif --calc=A --overwrite --outfile C:\Users\dbaston\AppData\Local\Temp\pytest-of-dbaston\pytest-5\test_gdal_calc_py_7a___0\out.tif

Calling gdal_calc with --optfile is successful:

C:\dev\gdal\build>python swig\python\osgeo_utils\gdal_calc.py --optfile C:\Users\dbaston\AppData\Local\Temp\pytest-of-dbaston\pytest-5\test_gdal_calc_py_7a___0\opt
0...10...20...30...40...50...60...70...80...90...100 - done.

Calling gdal_calc with @opt fails -- the \ characters appear to be stripped on reading:

C:\dev\gdal\build>python swig\python\osgeo_utils\gdal_calc.py @C:\Users\dbaston\AppData\Local\Temp\pytest-of-dbaston\pytest-5\test_gdal_calc_py_7a___0\opt
Could not open file "C:UsersdbastonAppDataLocalTemppytest-of-dbastonpytest-5gdal_calc0stefan_full_rgba.tif": No such file or directory

After editing the optfile to replace \ with /, it can be used with @:

C:\dev\gdal\build>python swig\python\osgeo_utils\gdal_calc.py @C:\Users\dbaston\AppData\Local\Temp\pytest-of-dbaston\pytest-5\test_gdal_calc_py_7a___0\opt2.txt
0...10...20...30...40...50...60...70...80...90...100 - done.

I'm going to skip the test on Windows for now.