diff: support unw/off - timeseries (#1011)

+ `diff.py`:
   - support the differencing between a *.unw (or offset file with FILE_TYPE of displacement) file and a time-series file, as used frequently in phase correction procedures, by adding a sub-function `diff_ifgram_and_timeseries()`
   - split `diff_timeseries()` and `diff_ifgram_stack()` out of `diff_file()` for clarity.
   - prepare isce metadata file, to be consistent with mask.py and subset.py

+ call `diff.py` to handle the correction procedure in the following scripts:
   - iono_tec.py
   - legacy/tropo_pyaps.py
   - solid_earth_tides.py
   - tropo_gacos.py
   - tropo_pyaps3.py

+ `cli/geocode.py`: if `--lat-file` is specified, honor this manually set file as the default lookupFile, rather than searching for the default file patterns, which could be NOT consistent with input files.

Author: yunjunz

src/mintpy/cli/diff.py

@@ -18,6 +18,7 @@
   diff.py  timeseries.h5  inputs/ERA5.h5  -o timeseries_ERA5.h5  --force
   diff.py  timeseries_ERA5_ramp_demErr.h5  ../GIANT/Stack/LS-PARAMS.h5 -o mintpy_giant.h5
   diff.py  reconUnwrapIfgram.h5  ./inputs/ifgramStack.h5  -o diffUnwrapIfgram.h5
+  diff.py  filt_20220905_20230220.unw  ./inputs/ERA5.h5 -o filt_20220905_20230220_ERA5.unw
 
   # multiple files
   diff.py  waterMask.h5  maskSantiago.h5  maskFernandina.h5  -o maskIsabela.h5
@@ -51,7 +52,7 @@ def cmd_line_parse(iargs=None):
     # check
     # check: number of files == 2 for time-series and ifgram stack
     ftype = readfile.read_attribute(inps.file1)['FILE_TYPE']
-    if ftype in ['timeseries', 'ifgramStack']:
+    if ftype in ['timeseries', 'ifgramStack', '.unw']:
         if len(inps.file2) > 1:
             raise SystemExit(f'ERROR: ONLY ONE file2 is inputed for {ftype} type!')
 

src/mintpy/cli/geocode.py

@@ -127,13 +127,13 @@ def cmd_line_parse(iargs=None):
 
     # check: --lookup (lookup table existence)
     if not inps.lookupFile:
-        # grab default lookup table
-        inps.lookupFile = ut.get_lookup_file(inps.lookupFile)
-
         # use isce-2 lat/lon.rdr file
         if not inps.lookupFile and inps.latFile:
             inps.lookupFile = inps.latFile
 
+        # grab default lookup table
+        inps.lookupFile = ut.get_lookup_file(inps.lookupFile)
+
         # final check
         if not inps.lookupFile:
             raise FileNotFoundError('No lookup table found! Can not geocode without it.')