improve README.md (with ipfs support)

README.md

-eget is a wget like downloader wrapper. It supports download urls with wildcard.
+# eget is a wget like downloader wrapper
 
-It supports wget or curl as backend.
+eget - wget like downloader wrapper with wildcard support in filename part of URL
+
+It supports download urls with wildcard. It supports wget or curl as backend.
+
+Basic usage:
+```
+eget [options] http://somesite.ru/dir/file.log
+```
+or with wildcard in filename:
+```
+eget [options] http://somesite.ru/dir/na*.log
+```
+or with file mask for site page search:
+```
+eget [options] http://somesite.ru/page na*.log
+```
+latest form will retrieve the site page source, search for ahref with file by file mask and print out found url(s).
 
 Options:
--q       - quiet mode"
+```
+    -q                        - quiet mode
+    -k|--no-check-certificate - skip SSL certificate chain support
+    -U|-A|--user-agent        - send browser like UserAgent
+    -4|--ipv4|--inet4-only    - use only IPV4
+    -6|--ipv6|--inet6-only    - use only IPV6
+    -O-|-O -                  - output downloaded file to stdout
+    -O file                   - download to this file
+    --latest                  - print only latest version of a file
+    --second-latest           - print only second to latest version of a file
+    --allow-mirrors           - check mirrors if url is not accessible
+ 
+    --list|--list-only        - print only URLs
+    --check URL               - check if the URL is accessible (returns HTTP 200 OK)
+    --get-response URL        - get response with all headers (ever if HEAD is not acceptable)
+    --get-filename URL        - print filename for the URL (via Content-Disposition if applicable)
+    --get-real-url URL        - print URL after all redirects
+```
+
+Supported URLs:
+```
+ftp:// http:// https:// file:/ ipfs://
+```
+
+Supported backends (set like EGET_BACKEND=curl)
+```
+wget curl (todo: aria2c)
+```
+
+## Examples:
+```
+$ eget http://example.com/e/* - download all files in e/ dir
+$ eget http://example.com/list *.txt - download all *.txt files listed at list page
+$ eget --list --latest https://github.com/deemru/chromium-gost/releases "chromium-gost-*linux-*" - download latest release by mask
+$ eget https://github.com/owner/project package*.ext
+$ eget -O myname ipfs://QmVRUjnsnxHWkjq91KreCpUk4D9oZEbMwNQ3rzdjwND5dR
+$ eget --check http://ftp.somesite.ru/test
+```
+
+## IPFS usage:
+
+Download file from IPFS:
+```
+$ eget [-O filename ] ipfs://QmYwf2GAMvHxfFiUFL2Mr6KUG6QrDiupqGc8ms785ktaYw
+```
+or URL with filename 
+```
+$ eget ipfs://QmXpKuc3NHFuyjd7fGgxKQVewZZ6V1iDECHCRPxAcQ9q2E?filename=brave-browser-beta-1.51.84-1.x86_64.rpm
+```
+
+just download as regular file.
 
--k|--no-check-certificate - skip SSL certificate chain support"
+## Usage EGET IPFS DB:
+```
+$ EGET_IPFS_DB=/path/to/file.txt eget http://somesite.ru/somefile.dat
+```
 
--U|-A|--user-agent - send browser like UserAgent"
+if the URL already exists in EGET IPFS DB, it will download via IPFS, otherwise it will download in a usual way and put to IPFS and EGET IPFS DB after it.
 
--O file  - download to this file (use filename from server if missed)"
+## IPFS related environment variables:
+```
+EGET_IPFS={disabled,auto,brave,local,gateway}
+```
+disabled by default (auto if EGET_IPFS_DB is set)
+auto will check brave, local, gateway
 
---list   - print files from url with mask"
+```
+EGET_IPFS_DB=/path/to/file.txt
+```
+file with text database of URL CID filename accordance
 
---latest - print only latest version of file"
+```
+EGET_IPFS_API=
+```
+set IPFS api for ipfs command, by default `/ip4/127.0.0.1/tcp/5001`
 
+```
+EGET_IPFS_GATEWAY=
+```
+http(s) gateway for download ipfs if there is no ipfs command and local sources
+default: https://cloudflare-ipfs.com/ipfs
 
-Examples:
-  $ eget http://example.com/e/* - download all files in e/ dir
-  $ eget http://example.com/list *.txt - download all *.txt files listed at list page
-  $ eget --list --latest https://github.com/deemru/chromium-gost/releases "chromium-gost-*linux-*" - download latest release by mask
+# Common environment variables:
+```
+EGET_BACKEND= curl or wget
+```
 
 See also: