Here is a list of all files with brief descriptions:

brin_2d.c
brin_common.c
brin_nd.c
bytebuffer.c
bytebuffer.h
cu_algorithm.c
cu_band_basics.c
cu_band_misc.c
cu_band_stats.c
cu_buildarea.c
cu_bytebuffer.c
cu_chaikin.c
cu_clean.c
cu_clip_by_rect.c
cu_effectivearea.c
cu_filterm.c
cu_force_sfs.c
cu_gdal.c
cu_geodetic.c
cu_geodetic_data.h
cu_geos.c
cu_geos_cluster.c
cu_homogenize.c
cu_in_encoded_polyline.c
cu_in_geojson.c
cu_in_twkb.c
cu_in_wkb.c
cu_in_wkt.c
cu_iterator.c
cu_libgeom.c
cu_lwstroke.c
cu_mapalgebra.c
cu_measures.c
cu_minimum_bounding_circle.c
liblwgeom/cunit/cu_misc.c
raster/test/cunit/cu_misc.c
cu_node.c
cu_out_encoded_polyline.c
cu_out_geojson.c
cu_out_gml.c
cu_out_kml.c
cu_out_svg.c
cu_out_twkb.c
cu_out_wkb.c
cu_out_wkt.c
cu_out_x3d.c
cu_pgsql2shp.c
cu_pgsql2shp.h
cu_pixtype.c
cu_print.c
cu_ptarray.c
cu_raster_basics.c
cu_raster_geometry.c
cu_raster_misc.c
cu_raster_wkb.c
cu_sfcgal.c
cu_shp2pgsql.c
cu_shp2pgsql.h
cu_spatial_relationship.c
cu_split.c
cu_stringbuffer.c
cu_surface.c
cu_surface.h
liblwgeom/cunit/cu_tester.c
loader/cunit/cu_tester.c
raster/test/cunit/cu_tester.c
liblwgeom/cunit/cu_tester.h
loader/cunit/cu_tester.h
raster/test/cunit/cu_tester.h
cu_tree.c
cu_triangulate.c
cu_unionfind.c
cu_varint.c
cu_wrapx.c
dbfopen.c
effectivearea.c
effectivearea.h
g_box.c
g_serialized.c
g_util.c
genraster.py
geobuf.c
geobuf.h
geography.h
geography_btree.c
geography_centroid.c
geography_inout.c
geography_measurement.c
geography_measurement_trees.c
geography_measurement_trees.h
geometry_inout.c
getopt.c
getopt.h
gserialized_estimate.c
gserialized_gist_2d.c
gserialized_gist_nd.c
gserialized_spgist_2d.c
gserialized_spgist_3d.c
gserialized_spgist_3d.h
gserialized_typmod.c
liblwgeom.h	This library is the generic geometry handling section of PostGIS
liblwgeom_internal.h
liblwgeom_topo.h
liblwgeom_topo_internal.h
librtcore.h	This library is the generic raster handling section of PostGIS
librtcore_internal.h
long_xact.c
lwalgorithm.c
lwboundingcircle.c
lwchaikins.c
lwcircstring.c
lwcollection.c
lwcompound.c
lwcurvepoly.c
lwgeodetic.c
lwgeodetic.h
lwgeodetic_tree.c
lwgeodetic_tree.h
lwgeom.c
lwgeom_accum.c	Versions of PostgreSQL < 8.4 perform array accumulation internally using pass by value, which is very slow working with large/many geometries
lwgeom_api.c
lwgeom_backend_api.c
lwgeom_backend_api.h
lwgeom_box.c
lwgeom_box3d.c
lwgeom_box3d.h
lwgeom_btree.c
lwgeom_debug.c
lwgeom_dump.c
lwgeom_dumppoints.c
lwgeom_export.c	Commons functions for all export functions
lwgeom_export.h
lwgeom_functions_analytic.c
lwgeom_functions_analytic.h
lwgeom_functions_basic.c
lwgeom_functions_lrs.c
lwgeom_functions_temporal.c
postgis/lwgeom_geos.c
liblwgeom/lwgeom_geos.c
postgis/lwgeom_geos.h
liblwgeom/lwgeom_geos.h
postgis/lwgeom_geos_clean.c
liblwgeom/lwgeom_geos_clean.c
lwgeom_geos_cluster.c
lwgeom_geos_node.c
lwgeom_geos_prepared.c
lwgeom_geos_prepared.h
lwgeom_geos_relatematch.c
lwgeom_geos_split.c
lwgeom_in_encoded_polyline.c
lwgeom_in_geohash.c
lwgeom_in_geojson.c
lwgeom_in_gml.c
lwgeom_in_kml.c
lwgeom_inout.c
lwgeom_log.h
lwgeom_median.c
lwgeom_ogc.c
lwgeom_out_geobuf.c	Geobuf export functions
lwgeom_out_mvt.c
lwgeom_rectree.c
lwgeom_rtree.c
lwgeom_rtree.h
postgis/lwgeom_sfcgal.c
liblwgeom/lwgeom_sfcgal.c
postgis/lwgeom_sfcgal.h
liblwgeom/lwgeom_sfcgal.h
lwgeom_spheroid.c
lwgeom_sqlmm.c
lwgeom_topo.c
postgis/lwgeom_transform.c
liblwgeom/lwgeom_transform.c
lwgeom_triggers.c	The intended use for this trigger function is making a geometry field cache it's bbox
lwgeom_window.c
lwgeom_wrapx.c
lwhomogenize.c
lwin_encoded_polyline.c
lwin_geojson.c
lwin_twkb.c
lwin_wkb.c
lwin_wkt.c
lwin_wkt.h
lwin_wkt_lex.c
lwin_wkt_parse.c
lwin_wkt_parse.h
lwiterator.c
lwkmeans.c
lwline.c
lwlinearreferencing.c
lwmcurve.c
lwmline.c
lwmpoint.c
lwmpoly.c
lwmsurface.c
lwmval.c
lwout_encoded_polyline.c
lwout_geojson.c
lwout_gml.c
lwout_kml.c
lwout_svg.c	SVG output routines
lwout_twkb.c
lwout_twkb.h
lwout_wkb.c
lwout_wkt.c
lwout_x3d.c
lwout_x3d.h
lwpoint.c
lwpoly.c
lwprint.c
lwpsurface.c
lwspheroid.c
lwstroke.c
lwtin.c
lwtree.c
lwtree.h
lwtriangle.c
lwunionfind.c
lwunionfind.h
lwutil.c
measures.c
measures.h
measures3d.c
measures3d.h
mvt.c
mvt.h
ovdump.py
pgsql2shp-cli.c
pgsql2shp-core.c
pgsql2shp-core.h
pixval.py
postgis_brin.h
postgis_libprotobuf.c
postgis_module.c
ptarray.c
raster2pgsql.c
raster2pgsql.h
raster2pgsql.py
rt_band.c
rt_context.c
rt_geometry.c
rt_mapalgebra.c
rt_pixel.c
rt_raster.c
rt_serialize.c
rt_serialize.h
rt_spatial_relationship.c
rt_statistics.c
rt_util.c
rt_warp.c
rt_wkb.c
rtgdalraster.py
rtpg_band_properties.c
rtpg_create.c
rtpg_gdal.c
rtpg_geometry.c
rtpg_inout.c
rtpg_internal.c
rtpg_internal.h
rtpg_mapalgebra.c
rtpg_pixel.c
rtpg_raster_properties.c
rtpg_spatial_relationship.c
rtpg_statistics.c
rtpg_utility.c
rtpg_wkb.c
rtpixdump.py
rtpostgis.c
rtpostgis.h
rtreader.py
rtrowdump.py
safileio.c
shapefil.h
shp2pgsql-cli.c
shp2pgsql-core.c
shp2pgsql-core.h
shp2pgsql-gui.c
shpcommon.c
shpcommon.h
shpopen.c
sqldefines.h
stringbuffer.c
stringbuffer.h
uthash.h
varint.c
varint.h
window.py